Indigenous hydrocarbon-utilizing bacterioflora in oil-polluted habitats in Kuwait, two decades after the greatest man-made oil spill

Microbial alchemists: unveiling the hidden potentials of halophilic organisms for soil restoration

Salinity, resulting from various contaminants, is a major concern to global crop cultivation. Soil salinity results in increased osmotic stress, oxidative stress, specific ion toxicity, nutrient deficiency in plants, groundwater contamination, and negative impacts on biogeochemical cycles. Leaching, the prevailing remediation method, is expensive, energy-intensive, demands more fresh water, and also causes nutrient loss which leads to infertile cropland and eutrophication of water bodies. Moreover, in soils co-contaminated with persistent organic pollutants, heavy metals, and textile dyes, leaching techniques may not be effective. It promotes the adoption of microbial remediation as an effective and eco-friendly method. Common microbes such as Pseudomonas, Trichoderma, and Bacillus often struggle to survive in high-saline conditions due to osmotic stress, ion imbalance, and protein denaturation. Halophiles, capable of withstanding high-saline conditions, exhibit a remarkable ability to utilize a broad spectrum of organic pollutants as carbon sources and restore the polluted environment. Furthermore, halophiles can enhance plant growth under stress conditions and produce vital bio-enzymes. Halophilic microorganisms can contribute to increasing soil microbial diversity, pollutant degradation, stabilizing soil structure, participating in nutrient dynamics, bio-geochemical cycles, enhancing soil fertility, and crop growth. This review provides an in-depth analysis of pollutant degradation, salt-tolerating mechanisms, and plant-soil-microbe interaction and offers a holistic perspective on their potential for soil restoration.

Everything Is Everywhere: Physiological Responses of the Mediterranean Sea and Eastern Pacific Ocean Epiphyte Cobetia Sp. to Varying Nutrient Concentration

Bacteria are essential in the maintenance and sustainment of marine environments (e.g., benthic systems), playing a key role in marine food webs and nutrient cycling. These microorganisms can live associated as epiphytic or endophytic populations with superior organisms with valuable ecological functions, e.g., seagrasses. Here, we isolated, identified, sequenced, and exposed two strains of the same species (i.e., identified as Cobetia sp.) from two different marine environments to different nutrient regimes using batch cultures: (1) Cobetia sp. UIB 001 from the endemic Mediterranean seagrass Posidonia oceanica and (2) Cobetia sp. 4B UA from the endemic Humboldt Current System (HCS) seagrass Heterozostera chilensis. From our physiological studies, both strains behaved as bacteria capable to cope with different nutrient and pH regimes, i.e., N, P, and Fe combined with different pH levels, both in long-term (12 days (d)) and short-term studies (4 d/96 h (h)). We showed that the isolated strains were sensitive to the N source (inorganic and organic) at low and high concentrations and low pH levels. Low availability of phosphorus (P) and Fe had a negative independent effect on growth, especially in the long-term studies. The strain UIB 001 showed a better adaptation to low nutrient concentrations, being a potential N₂-fixer, reaching higher growth rates (μ) than the HCS strain. P-acquisition mechanisms were deeply investigated at the enzymatic (i.e., alkaline phosphatase activity, APA) and structural level (e.g., alkaline phosphatase D, PhoD). Finally, these results were complemented with the study of biochemical markers, i.e., reactive oxygen species (ROS). In short, we present how ecological niches (i.e., MS and HCS) might determine, select, and modify the genomic and phenotypic features of the same bacterial species (i.e., Cobetia spp.) found in different marine environments, pointing to a direct correlation between adaptability and oligotrophy of seawater.

Highly Contaminated Marine Sediments Can Host Rare Bacterial Taxa Potentially Useful for Bioremediation

Coastal areas impacted by high anthropogenic pressures typically display sediment contamination by polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). Microbial-based bioremediation represents a promising strategy for sediment reclamation, yet it frequently fails due to poor knowledge of the diversity and dynamics of the autochthonous microbial assemblages and to the inhibition of the target microbes in the contaminated matrix. In the present study, we used an integrated approach including a detailed environmental characterization, high-throughput sequencing and culturing to identify autochthonous bacteria with bioremediation potential in the sediments of Bagnoli-Coroglio (Gulf of Naples, Mediterranean Sea), a coastal area highly contaminated by PAHs, aliphatic hydrocarbons and HMs. The analysis of the benthic prokaryotic diversity showed that the distribution of the dominant taxon (Gammaproteobacteria) was mainly influenced by PAHs, As, and Cd concentrations. The other abundant taxa (including Alphaproteobacteria, Deltaproteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, NB1-j, Desulfobacterota, and Myxococcota) were mainly driven by sediment grain size and by Cu and Cr concentrations, while the rare taxa (i.e., each contributing <1%) by As and aliphatic hydrocarbons concentrations and by sediment redox potential. These results suggest a differential response of bacterial taxa to environmental features and chemical contamination and those different bacterial groups may be inhibited or promoted by different contaminants. This hypothesis was confirmed by culturing and isolating 80 bacterial strains using media highly enriched in PAHs, only nine of which were contextually resistant to high HM concentrations. Such resistant isolates represented novel Gammaproteobacteria strains affiliated to Vibrio, Pseudoalteromonas, and Agarivorans, which were only scarcely represented in their original assemblages. These findings suggest that rare but culturable bacterial strains resistant/tolerant to high levels of mixed contaminants can be promising candidates useful for the reclamation by bioaugmentation strategies of marine sediments that are highly contaminated with PAHs and HMs.

Crude oil pollution and biodegradation at the Persian Gulf: A comprehensive and review study

The Persian Gulf consider as the fundamental biological marine condition between the seas. There is a different assortment of marine life forms including corals, wipes, and fish in this marine condition. Mangrove timberlands are found all through this sea-going biological system. Sullying of the Persian Gulf to oil-based goods is the principle of danger to this marine condition and this contamination can effectively affect this differing marine condition. Numerous specialists examined the result of oil contamination on Persian Gulf marine creatures including corals sponges, bivalves, and fishes. These analysts affirmed this oil contamination on the Persian Gulf significantly diminished biodiversity. Diverse microorganisms fit to consume oil-based commodities detailed by various scientists from the Persian Gulf and their capacity to the debasement of unrefined petroleum has been examined. There has additionally been little exploration of cyanobacteria, yeast, and unrefined petroleum debasing organisms in this sea-going environment. Biosurfactants are amphipathic molecules that upgrade the disintegration of oil and increment their bioavailability to corrupt microscopic organisms. Additionally, biosurfactant-producing bacteria were discovered from the Persian Gulf, and the capability to degradation of crude oil in microscale was evaluated. The current review article aims to collect the finding of various researches performed in the Persian Gulf on oil pollution and crude-oil biodegradation. It is expected that by applying biological methods in combination with mechanical and chemical methods, the hazard consequences of crude-oil contamination on this important aquatic ecosystem at the world will be mitigated and a step towards preserving this diverse marine environment.

Hydrocarbon-Degrading Bacteria Alcanivorax and Marinobacter Associated With Microalgae Pavlova lutheri and Nannochloropsis oculata

Marine hydrocarbon-degrading bacteria play an important role in natural petroleum biodegradation processes and were initially associated with man-made oil spills or natural seeps. There is no full clarity though on what, in the absence of petroleum, their natural niches are. Few studies pointed at some marine microalgae that produce oleophilic compounds (alkanes, long-chain fatty acids, and alcohols) as potential natural hosts of these bacteria. We established Dansk crude oil-based enrichment cultures with photobioreactor-grown marine microalgae cultures Pavlova lutheri and Nannochloropsis oculata and analyzed the microbial succession using cultivation and SSU (16S) rRNA amplicon sequencing. We found that petroleum enforced a strong selection for members of Alpha- and Gamma-proteobacteria in both enrichment cultures with the prevalence of Alcanivorax and Marinobacter spp., well-known hydrocarbonoclastic bacteria. In total, 48 non-redundant bacterial strains were isolated and identified to represent genera Alcanivorax, Marinobacter, Thalassospira, Hyphomonas, Halomonas, Marinovum, Roseovarius, and Oleibacter, which were abundant in sequencing reads in both crude oil enrichments. Our assessment of public databases demonstrated some overlaps of geographical sites of isolation of Nannochloropsis and Pavlova with places of molecular detection and isolation of Alcanivorax and Marinobacter spp. Our study suggests that these globally important hydrocarbon-degrading bacteria are associated with P. lutheri and N. oculata.

Oleiliquidispirillum nitrogeniifigens gen. nov., sp. nov., a new member of the family Rhodospirillaceae isolated from oil reservoir water

A novel Gram-staining-negative, spiral-shaped bacterium, designated strain 64-1^T, was isolated from oil reservoir water collected from Liaohe oilfield, north-eastern China. Growth occurred at 15-55 °C and pH 6.0-10.0. The sole respiratory quinone was Q-10. The predominant cellular fatty acids were summed feature 8 (C_18 : 1  ω7c /C_18 : 1  ω6c), C_16 : 0 and C_19 : 0 cyclo ω8c. The polar lipids consisted of phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylcholine (PC), an unidentified aminophospholipid (UAPL), an unidentified aminolipid (UAL) and two unidentified polar lipids (UPL). The genomic DNA G+C content of strain 64-1^T was 64.5 mol%. Strain 64-1^T shared the highest 16S rRNA gene sequence similarities with Phaeospirillum chandramohanii JA145^T (92.0 %) and Telmatospirillum siberiense 26-4b1^T (91.8 %). In the phylogenetic trees, the strain constituted a sub-cluster within the family Rhodospirillaceae. Based on the results of morphological, physiological, biochemical and phylogenetic analysis, strain 64-1^T represents a new species of a novel genus within the family Rhodospirillaceae, for which the name Oleiliquidispirillum nitrogeniifigens gen. nov., sp. nov. is proposed. The type strain is 64-1^T (=CGMCC 1.16798^T=LMG 31399^T).

Plant-based oil-sorbents harbor native microbial communities effective in spilled oil-bioremediation under nitrogen starvation and heavy metal-stresses

Cultivation on selective media revealed that the oil-sorbents, wheat straw, corncobs and sugarcane bagasse harbor hydrocarbonoclastic, diazotrophic and heavy metal-resistant microorganisms. Nitrogen-free media containing 1.0% crude oil lost between 32.2 and 37.5% of this oil, after 8 months when they have been inoculated with such microorganism-loaded sorbents. The used wheat straw, corncobs and sugarcane bagasse samples, 1.0 g each, absorbed respectively, 1.9, 1.1 and 2.5 g oil samples, and lost 24.3-39.2% of these amounts, after they had been incubated for 8 months. Total genomic DNA's from culture media and sorbents revealed various nitrogenase-coding nifH-genes. Pure hydrocarbonoclastic microbial isolates tolerated certain concentrations of, Hg²⁺, Cd²⁺, Pb²⁺, AsO₄^3- and AsO₃^3-. Some of those isolates even grew excellently with up to 1000 ppm of Pb²⁺ and 36,000 ppm of AsO₄^3- also in the presence of oil. Tested strains removed the tested heavy metals, Hg²⁺, Cd²⁺ and Pb²⁺ from the media and thus, reduced their toxicity against the hydrocarbon-degraders. It was concluded that plant-based sorbents, not only remove oil physically, but also harbor microbial communities effective in spilled oil-bioremediation under multiple stresses. Although each community consisted of one to three species only, the consortia which reached in numbers millions of CFU ml^-1 enrich the oily media with fixed nitrogen, and remove heavy metals which otherwise inhibit the oil-degrading microorganisms.

Isolation of novel quorum-sensing active bacteria from microbial mats in Shark Bay Australia

Quorum sensing is a potent system of genetic control allowing phenotypes to be coordinated across localized communities. In this study, quorum sensing systems in Shark Bay microbial mats were delineated using a targeted approach analyzing whole mat extractions as well as the creation of an isolate library. A library of 165 isolates from different mat types were screened using the AHL biosensor E. coli MT102. Based on sequence identity 30 unique isolates belonging to Proteobacteria, Actinobacteria and Firmicutes were found to activate the AHL biosensor, suggesting AHLs or analogous compounds were potentially present. Several of the isolates have not been shown previously to produce signal molecules, particularly the members of the Actinobacteria and Firmicutes phyla including Virgibacillus, Halobacillius, Microbacterium and Brevibacterium. These active isolates were further screened using thin-layer chromatography (TLC) providing putative identities of AHL molecules present within the mat communities. Nine isolates were capable of producing several spots of varying sizes after TLC separation, suggesting the presence of multiple signalling molecules. This study is the first to delineate AHL-based signalling in the microbial mats of Shark Bay, and suggests quorum sensing may play a role in the ecosphysiological coordination of complex phenotypes across microbial mat communities.

Ability of the So-Called Obligate Hydrocarbonoclastic Bacteria to Utilize Nonhydrocarbon Substrates Thus Enhancing Their Activities Despite their Misleading Name

BACKGROUND

The group of the so-called obligate hydrocarbonoclastic bacteria (OHCB) are marine microorganisms affiliated with the genera Alcanivorax, Cycloclasticus, Oleiphilus and Thalassolituus. This small group plays a major role in oil-bioremediation in marine ecosystems. Marinobacter and Planomicrobium are considered related to this group. The OHCB are claimed to be obligate to hydrocarbon nutrition. This study argues against this claim.

RESULTS

Four Alcanivorax species, three Marinobacter species and Planomicrobium okeanokoites from the Arabian/Persian Gulf proved to be not obligate to hydrocarbon nutrition. Although the eight strains grew on crude oil, n-octadecane and phenanthrene as sole carbon substrates, their growth was weaker than on certain nonhydrocarbon, organic compounds viz. peptone, glutamic acid, pyruvic acid, sucrose, mannose and others. Glucose and lactose failed to support the growth of seven of the eight tested strains. Mannose was utilized by five and sucrose by six strains. The well-known intermediate metabolite; pyruvic acid was utilized by all the eight strains, and lactic acid by five strains. In batch cultures, all the tested species consumed higher proportions of peptone than of n-alkanes and phenanthrene. When peptone and crude oil were provided together into the medium, the OHCB started to consume peptone first, and the enriched bacterial populations consumed oil effectively. Added nonhydrocarbon substrates biostimulated oil-consumption by all OHCB species.

CONCLUSION

The tested OHCB species are not obligate hydrocarbon-utilizers. This provides them with the merit of survival, should their marine ecosystems become oil- or hydrocarbon-free. The fact that conventional, organic substrates biostimulated hydrocarbon-consumption by the tested bacterial species confirms the facultative nature of those organisms and is interesting from the practical point of view.

Vertical stratification of bacteria and the chemical compounds in crude oil-contaminated soil layers of the semi-deserted Dzungharian Basin

The largely semi-deserted and deserted Dzungharian Basin sites in the northwest of China geologically represent an extension of the Paleozoic Kazakhstan Block and were once part of an independent continent. For reasons of overdevelopment and unreasonable operations during the process of exploitation and transportation, oil pollutants that were discharged into the soil environment caused serious pollution in this weak ecosystem. To explore the bacterial community composition in detail and their possible origination and potential during the natural attenuation of petroleum contaminants in this type of ecologic niche, GC-MS and high-throughput sequencing techniques were used to resolve the organic compounds and bacterial communities in vertical soil layers. The degradation of petroleum contaminants in semi-deserted and deserted soils mainly occurred in the layer at a depth of 45-55 cm. During this process, aromatic and heterocyclic compounds were significantly enriched in soils. The bacterial communities in this basin exhibited a distinct vertical stratification from the surface layer down to the bottom soil layer. Considering the interaction between the community composition and the geochemical properties, we speculate that the degradation of petroleum contaminants in this semi-deserted and deserted soil might represent a microorganism-mediated process and mainly occur in the deeper soil layer.

Bioremediation of oil-based drill cuttings by a halophilic consortium isolated from oil-contaminated saline soil

Oil-based drill cuttings are hazardous wastes containing complex hydrocarbons, heavy metals, and brine. Their remediation is a crucial step before release to the environment. In this work, we enriched a halophilic consortium, from oil-polluted saline soil, which is capable of degrading diesel as the main pollutant of oil-based drill cuttings. The degradation ability of the consortium was evaluated in microcosms using two different diluting agents (fine sand and biologically active soil). During the bioremediation process, the bacterial community dynamics of the microcosms was surveyed using PCR amplification of a fragment of 16S rRNA gene followed by denaturing gradient gel electrophoresis (DGGE). The diesel degradation rates were monitored by total petroleum hydrocarbon (TPH) measurement and the total count of heterotrophic and diesel-degrading bacteria. After 3 months, the microcosm containing fine sand and drill cuttings with the ratio of 1:1 (initial TPH of 36,000 mg/kg) showed the highest TPH removal (40%) and its dominant bacterial isolates belonged to the genera Dietzia, Arthrobacter, and Halomonas. DGGE results also confirmed the role of these genera in drill cuttings remediation. DGGE analysis of the bacterial diversity showed that Propionibacterium, Salinimicrobium, Marinobacter, and Dietzia are dominant in active soil microcosm; whereas Bacillus, Salinibacillus, and Marinobacter are abundant in sand microcosm. Our results suggest that the bioaugmentation strategy would be more successful if the diluting agent does not contain a complex microbial community.

Culture-independent analysis of hydrocarbonoclastic bacterial communities in environmental samples during oil-bioremediation

To analyze microbial communities in environmental samples, this study combined Denaturing Gradient Gel Electrophoresis of amplified 16S rRNA-genes in total genomic DNA extracts from those samples with gene sequencing. The environmental samples studied were oily seawater and soil samples, that had been bioaugmented with natural materials rich in hydrocarbonoclastic bacteria. This molecular approach revealed much more diverse bacterial taxa than the culture-dependent method we had used in an earlier study for the analysis of the same samples. The study described the dynamics of bacterial communities during bioremediation. The main limitation associated with this molecular approach, namely of not distinguishing hydrocarbonoclastic taxa from others, was overcome by consulting the literature for the hydrocarbonoclastic potential of taxa related to those identified in this study. By doing so, it was concluded that the hydrocarbonoclastic bacterial taxa were much more diverse than those captured by the culture-dependent approach. The molecular analysis also revealed the frequent occurrence of nifH-genes in the total genomic DNA extracts of all the studied environmental samples, which reflects a nitrogen-fixation potential. Nitrogen fertilization is long known to enhance microbial oil-bioremediation. The study revealed that bioaugmentation using plant rhizospheres or soil with long history of oil-pollution was more effective in oil-removal in the desert soil than in seawater microcosms.

Gelatinizing oil in water and its removal via bacteria inhabiting the gels

When crude oil samples were shaken (200 rpm) in seawater samples from the Arabian Gulf at 30 °C, usually oil-gels were produced spontaneously leaving the water quite clear. The gelators could probably be based on cholesteryl derivatives. Microscopic examination of the established gels revealed nanofibrellar structures similar to those described by earlier workers for artificially synthesized gelators. Communities of bacteria including prosthetic and stalked members as well as oil-degrading bacteria were recorded in such gels. Chemical analysis revealed that 88.5% of the oil entrapped by gelation was biodegraded after 40 days at 30 °C. Individual bacterial species isolated from the oil-gels biodegraded in batch cultures between 17.8 and 33.3% of the oil added at time zero in 12 days at 30 °C. Gelation is a promising approach, not only for clean, physical removal of oil spilled in aquatic habitats, as so far suggested, but also in its effective microbiological biodegradation, as the current study revealed.

Oil uptake by plant-based sorbents and its biodegradation by their naturally associated microorganisms

The plant waste-products, wheat straw, corn-cobs and sugarcane bagasse took up respectively, 190, 110 and 250% of their own weights crude oil. The same materials harbored respectively, 3.6 × 10⁵, 8.5 × 10³ and 2.3 × 10⁶ g^-1 cells of hydrocarbonoclastic microorganisms, as determined by a culture-dependent method. The molecular, culture-independent analysis revealed that the three materials were associated with microbial communities comprising genera known for their hydrocarbonoclastic activity. In bench-scale experiments, inoculating oily media with samples of the individual waste products led to the biodegradation of 34.0-44.9% of the available oil after 8 months. Also plant-product samples, which had been used as oil sorbents lost 24.3-47.7% of their oil via their associated microorganisms, when kept moist for 8 months. In this way, it is easy to see that those waste products are capable of remediating spilled oil physically, and that their associated microbial communities can degrade it biologically.

The Variable Influence of Dispersant on Degradation of Oil Hydrocarbons in Subarctic Deep-Sea Sediments at Low Temperatures (0-5 °C)

The microbial degradation of petroleum hydrocarbons at low temperatures was investigated in subarctic deep-sea sediments in the Faroe Shetland Channel (FSC). The effect of the marine oil dispersant, Superdispersant 25 on hydrocarbon degradation was also examined. Sediments collected at 500 and 1000 m depth were spiked with a model oil containing 20 hydrocarbons and incubated at ambient temperature (5 and 0 °C, respectively) with and without marine dispersant. Treatment of sediments with hydrocarbons resulted in the enrichment of Gammaproteobacteria, and specifically the genera Pseudoalteromonas, Pseudomonas, Halomonas, and Cobetia. Hydrocarbon degradation was faster at 5 °C (500 m) with 65–89% of each component degraded after 50 days compared to 0–47% degradation at 0 °C (1000 m), where the aromatic hydrocarbons fluoranthene, anthracene, and Dibenzothiophene showed no degradation. Dispersant significantly increased the rate of degradation at 1000 m, but had no effect at 500 m. There was no statistically significant effect of Superdispersant 25 on the bacterial community structure at either station. These results show that the indigenous bacterial community in the FSC has the capacity to mitigate some of the effects of a potential oil spill, however, the effect of dispersant is ambiguous and further research is needed to understand the implications of its use.

Capabilities and limitations of DGGE for the analysis of hydrocarbonoclastic prokaryotic communities directly in environmental samples

Prokaryotic communities in pristine and oil-contaminated desert soil, seawater, and hypersaline coastal soil were analyzed using culture-dependent and culture-independent approaches. The former technique was the dilution-plating method. For the latter, total genomic DNA was extracted and the 16S rRNA genes were amplified using a universal bacterial primer pair and primer pairs specific for Actinobacteria, Gammaproteobacteria, and Archaea. The amplicons were resolved using denaturing gradient gel electrophoresis (DGGE) and sequenced, and the sequences were compared to those in GenBank. The plating method offered the advantages of capturing the targeted hydrocarbonoclastic microorganisms, counting them and providing cultures for further study. However, this technique could not capture more than a total of 15 different prokaryotic taxa. Those taxa belonged predominantly to the genera Alcanivorax, Pseudoxanthomonas, Bosea, Halomonas, and Marinobacter. The individual isolates in culture consumed between 19 and 50% of the available crude oil in 10 days. Although the culture-independent approach revealed much more microbial diversity, it was not problem-free. The subdivision primers exhibited satisfactory specificity, but they failed to capture all the available taxa. The universal bacterial primer pair ignored Actinobacteria altogether, although the primer pair specific for Actinobacteria captured many of them, for example, the genera Geodermatophilus, Streptomyces, Mycobacterium, Pontimonas, Rhodococcus, Blastococcus, Kocuria, and many others. Because most researchers worldwide use universal primers for PCR, this finding should be considered critically to avoid misleading interpretations.

Lipid accumulation in prokaryotic microorganisms from arid habitats

This review shall provide support for the suitability of arid environments as preferred location to search for unknown lipid-accumulative bacteria. Bacterial lipids are attracting more and more attention as sustainable replacement for mineral oil in fuel and plastic production. The development of prokaryotic microorganisms in arid desert habitats is affected by its harsh living conditions. Drought, nutrient limitation, strong radiation, and extreme temperatures necessitate effective adaption mechanisms. Accumulation of storage lipids as energy reserve and source of metabolic water represents a common adaption in desert animals and presumably in desert bacteria and archaea as well. Comparison of corresponding literature resulted in several bacterial species from desert habitats, which had already been described as lipid-accumulative elsewhere. Based on the gathered information, literature on microbial communities in hot desert, cold desert, and humid soil were analyzed on its content of lipid-accumulative bacteria. With more than 50% of the total community size in single studies, hot deserts appear to be more favorable for lipid-accumulative species then humid soil (≤20%) and cold deserts (≤17%). Low bacterial lipid accumulation in cold deserts is assumed to result from the influence of low temperatures on fatty acids and the increased necessity of permanent adaption methods.

Bacterial community analysis of an industrial wastewater treatment plant in Colombia with screening for lipid-degrading microorganisms

The operation of wastewater treatment technologies depends on a combination of physical, chemical and biological factors. Microorganisms present in wastewater treatment plants play essential roles in the degradation and removal of organic waste and xenobiotic pollutants. Several microorganisms have been used in complementary treatments to process effluents rich in fats and oils. Microbial lipases have received significant industrial attention because of their stability, broad substrate specificity, high yields, and regular supply, as well as the fact that the microorganisms producing them grow rapidly on inexpensive media. In Colombia, bacterial community studies have focused on populations of cultivable nitrifying, heterotrophic and nitrogen-fixing bacteria present in constructed wetlands. In this study, culture-dependent methods, culture-independent methods (TTGE, RISA) and enzymatic methods were used to estimate bacterial diversity, to monitor temporal and spatial changes in bacterial communities, and to screen microorganisms that presented lipolytic activity. The dominant microorganisms in the Wastewater Treatment Plant (WWTP) examined in this study belonged to the phyla Firmicutes, Proteobacteria and Bacteroidetes. The enzymatic studies performed indicated that five bacterial isolates and three fungal isolates possessed the ability to degrade lipids; additionally, the Serratia, Kosakonia and Mucor genera presented lipase-mediated transesterification activity. The implications of these findings in regard to possible applications are discussed later in this paper. Our results indicate that there is a wide diversity of aerobic Gram-negative bacteria inhabiting the different sections of the WWTP, which could indicate its ecological condition, functioning and general efficiency.

Consistent Occurrence of Hydrocarbonoclastic Marinobacter Strains in Various Cultures of Picocyanobacteria from the Arabian Gulf: Promising Associations for Biodegradation of Marine Oil Pollution

Fifteen nonaxenic cultures of picocyanobacteria were isolated from the Arabian Gulf, from which 122 heterotrophic bacterial strains were obtained. Based on their 16S rRNA gene sequences, those strains were affiliated with 22 different species, 82.8% of which belonged to the genus Marinobacter, known to comprise hydrocarbonoclastic strains. The remaining species belonged to the genera Alcanivorax, Bacillus, Halomonas, Mesorhizobium, and Paenibacillus, and a Bacteriodetes bacterium also known to comprise hydrocarbonoclastic strains. All the picocyanobacterial cultures harbored one or more strains of Marinobacter. Marinobacter in addition to Alcanivorax and other genera isolated from those picocyanobacteria grew on Tween 80, crude oil, and pure hydrocarbons as sole sources of carbon and energy, i.e. they are related to the obligate hydrocarbonoclastic bacteria group. They consumed crude oil, n-octadecane, and phenanthrene in batch cultures. The results indicated that Marinobacter isolates seemed to grow better and consume more oil in the presence of their host picocyanobacteria than in their absence. Such natural microbial associations assumingly play a role in bioremediation of spilled hydrocarbons in the Arabian Gulf. Similar associations probably occur in other marine environments as well and are active in oil spill removal.

Autochthonous bioaugmentation with environmental samples rich in hydrocarbonoclastic bacteria for bench-scale bioremediation of oily seawater and desert soil

Oil-contaminated seawater and desert soil batches were bioaugmented with suspensions of pea (Pisum sativum) rhizosphere and soil with long history of oil pollution. Oil consumption was measured by gas-liquid chromatography. Hydrocarbonoclastic bacteria in the bioremediation batches were counted using a mineral medium with oil vapor as a sole carbon source and characterized by their 16S ribosomal RNA (rRNA)-gene sequences. Most of the oil was consumed during the first 2-4 months, and the oil-removal rate decreased or ceased thereafter due to nutrient and oxygen depletion. Supplying the batches with NaNO3 (nitrogen fertilization) at a late phase of bioremediation resulted in reenhanced oil consumption and bacterial growth. In the seawater batches bioaugmented with rhizospheric suspension, the autochthonous rhizospheric bacterial species Microbacterium oxidans and Rhodococcus spp. were established and contributed to oil-removal. The rhizosphere-bioaugmented soil batches selectively favored Arthrobacter nitroguajacolicus, Caulobacter segnis, and Ensifer adherens. In seawater batches bioaugmented with long-contaminated soil, the predominant oil-removing bacterium was the marine species Marinobacter hydrocarbonoclasticus. In soil batches on the other hand, the autochthonous inhabitants of the long-contaminated soil, Pseudomonas and Massilia species were established and contributed to oil removal. It was concluded that the use of rhizospheric bacteria for inoculating seawater and desert soil and of bacteria in long-contaminated soil for inoculating desert soil follows the concept of "autochthonous bioaugmentation." Inoculating seawater with bacteria in long-contaminated soil, on the other hand, merits the designation "allochthonous bioaugmentation."

Determination of the Residual Anthracene Concentration in Cultures of Haloalkalitolerant Actinomycetes by Excitation Fluorescence, Emission Fluorescence, and Synchronous Fluorescence: Comparative Study

Polycyclic aromatic hydrocarbons (PAHs) are compounds that can be quantified by fluorescence due to their high quantum yield. Haloalkalitolerant bacteria tolerate wide concentration ranges of NaCl and pH. They are potentially useful in the PAHs bioremediation of saline environments. However, it is known that salinity of the sample affects fluorescence signal regardless of the method. The objective of this work was to carry out a comparative study based on the sensitivity, linearity, and detection limits of the excitation, emission, and synchronous fluorescence methods, during the quantification of the residual anthracene concentration from the following haloalkalitolerant actinomycetes cultures Kocuria rosea, Kocuria palustris, Microbacterium testaceum, and 4 strains of Nocardia farcinica, in order to establish the proper fluorescence method to study the PAHs biodegrading capacity of haloalkalitolerant actinobacteria. The study demonstrated statistical differences among the strains and among the fluorescence methods regarding the anthracene residual concentration. The results showed that excitation and emission fluorescence methods performed very similarly but sensitivity in excitation fluorescence is slightly higher. Synchronous fluorescence using Δλ = 150 nm is not the most convenient method. Therefore we propose the excitation fluorescence as the fluorescence method to be used in the study of the PAHs biodegrading capacity of haloalkalitolerant actinomycetes.

Actinomycetes from the South China Sea sponges: isolation, diversity, and potential for aromatic polyketides discovery

Marine sponges often harbor dense and diverse microbial communities including actinobacteria. To date no comprehensive investigation has been performed on the culturable diversity of the actinomycetes associated with South China Sea sponges. Structurally novel aromatic polyketides were recently discovered from marine sponge-derived Streptomyces and Saccharopolyspora strains, suggesting that sponge-associated actinomycetes can serve as a new source of aromatic polyketides. In this study, a total of 77 actinomycete strains were isolated from 15 South China Sea sponge species. Phylogenetic characterization of the isolates based on 16S rRNA gene sequencing supported their assignment to 12 families and 20 genera, among which three rare genera (Marihabitans, Polymorphospora, and Streptomonospora) were isolated from marine sponges for the first time. Subsequently, β-ketoacyl synthase (KS_α) gene was used as marker for evaluating the potential of the actinomycete strains to produce aromatic polyketides. As a result, KS_α gene was detected in 35 isolates related to seven genera (Kocuria, Micromonospora, Nocardia, Nocardiopsis, Saccharopolyspora, Salinispora, and Streptomyces). Finally, 10 strains were selected for small-scale fermentation, and one angucycline compound was detected from the culture extract of Streptomyces anulatus strain S71. This study advanced our knowledge of the sponge-associated actinomycetes regarding their diversity and potential in producing aromatic polyketides.

Olive-pomace harbors bacteria with the potential for hydrocarbon-biodegradation, nitrogen-fixation and mercury-resistance: promising material for waste-oil-bioremediation

Olive-pomace, a waste by-product of olive oil industry, took up >40% of its weight crude oil. Meanwhile, this material harbored a rich and diverse hydrocarbonoclastic bacterial population in the magnitude of 10(6) to 10(7) cells g(-1). Using this material for bioaugmentation of batch cultures in crude oil-containing mineral medium, resulted in the consumption of 12.9, 21.5, 28.3, and 43% oil after 2, 4, 6 and 8 months, respectively. Similar oil-consumption values, namely 11.0, 29.3, 34.7 and 43.9%, respectively, were recorded when a NaNO3-free medium was used instead of the complete medium. Hydrocarbonoclastic bacteria involved in those bioremediation processes, as characterized by their 16S rRNA-gene sequences, belonged to the genera Agrococcus, Pseudomonas, Cellulosimicrobium, Streptococcus, Sinorhizobium, Olivibacter, Ochrobactrum, Rhizobium, Pleomorphomonas, Azoarcus, Starkeya and others. Many of the bacterial species belonging to those genera were diazotrophic; they proved to contain the nifH-genes in their genomes. Still other bacterial species could tolerate the heavy metal mercury. The dynamic changes of the proportions of various species during 8 months of incubation were recorded. The culture-independent, phylogenetic analysis of the bacterioflora gave lists different from those recorded by the culture-dependent method. Nevertheless, those lists comprised among others, several genera known for their hydrocarbonoclastic potential, e.g. Pseudomonas, Mycobacterium, Sphingobium, and Citrobacter. It was concluded that olive-pomace could be applied in oil-remediation, not only as a physical sorbent, but also for bioaugmentation purposes as a biological source of hydrocarbonoclastic bacteria.

Moderately thermophilic, hydrocarbonoclastic bacterial communities in Kuwaiti desert soil: enhanced activity via Ca(2+) and dipicolinic acid amendment

Pristine and oil-contaminated desert soil samples from Kuwait harbored between 10 and 100 cells g(-1) of hydrocarbonoclastic bacteria capable of growth at 50 °C. Enrichment by incubation of moistened soils for 6 months at 50 °C raised those numbers to the magnitude of 10(3) cells g(-1). Most of these organisms were moderately thermophilic and belonged to the genus Bacillus; they grew at 40-50 °C better than at 30 °C. Species belonging to the genera Amycolatopsis, Chelativorans, Isoptericola, Nocardia, Aeribacillus, Aneurinibacillus, Brevibacillus, Geobacillus, Kocuria, Marinobacter and Paenibacillus were also found. This microbial diversity indicates a good potential for hydrocarbon removal in soil at high temperature. Analysis of the same desert soil samples by a culture-independent method (combined, DGGE and 16S rDNA sequencing) revealed dramatically different lists of microorganisms, many of which had been recorded as hydrocarbonoclastic. Many species were more frequent in the oil contaminated than in the pristine soil samples, which may reflect their hydrocarbonoclastic activity in situ. The growth and hydrocarbon consumption potential of all tested isolates were dramatically enhanced by amendment of the cultures with Ca(2+) (up to 2.5 M CaSO4). This enhanced effect was even amplified when in addition 8 % w/v dipicolinic acid was amended. These novel findings are useful in suggesting biotechnologies for waste hydrocarbon remediation at moderately high temperature.

Most hydrocarbonoclastic bacteria in the total environment are diazotrophic, which highlights their value in the bioremediation of hydrocarbon contaminants

Eighty-two out of the 100 hydrocarbonoclastic bacterial species that have been already isolated from oil-contaminated Kuwaiti sites, characterized by 16S rRNA nucleotide sequencing, and preserved in our private culture collection, grew successfully in a mineral medium free of any nitrogenous compounds with oil vapor as the sole carbon source. Fifteen out of these 82 species were selected for further study based on the predominance of most of the isolates in their specific sites. All of these species tested positive for nitrogenase using the acetylene reduction reaction. They belonged to the genera Agrobacterium, Sphingomonas, and Pseudomonas from oily desert soil and Nesiotobacter, Nitratireductor, Acinetobacter, Alcanivorax, Arthrobacter, Marinobacter, Pseudoalteromonas, Vibrio, Diatzia, Mycobacterium, and Microbacterium from the Arabian/Persian Gulf water body. A PCR-DGGE-based sequencing analysis of nifH genes revealed the common occurrence of the corresponding genes among all the strains tested. The tested species also grew well and consumed crude oil effectively in NaNO₃ -containing medium with and without nitrogen gas in the top space. On the other hand, these bacteria only grew and consumed crude oil in the NaNO₃ -free medium when the top space gas contained nitrogen. We concluded that most hydrocarbonoclastic bacteria are diazotrophic, which allows for their wide distribution in the total environment. Therefore, these bacteria are useful for the cost-effective, environmentally friendly bioremediation of hydrocarbon contaminants.

Microbial responses to the Deepwater Horizon oil spill: from coastal wetlands to the deep sea

The Deepwater Horizon oil spill in the northern Gulf of Mexico represents the largest marine accidental oil spill in history. It is distinguished from past spills in that it occurred at the greatest depth (1,500 m), the amount of hydrocarbon gas (mostly methane) lost was equivalent to the mass of crude oil released, and dispersants were used for the first time in the deep sea in an attempt to remediate the spill. The spill is also unique in that it has been characterized with an unprecedented level of resolution using next-generation sequencing technologies, especially for the ubiquitous hydrocarbon-degrading microbial communities that appeared largely to consume the gases and to degrade a significant fraction of the petroleum. Results have shown an unexpectedly rapid response of deep-sea Gammaproteobacteria to oil and gas and documented a distinct succession correlated with the control of the oil flow and well shut-in. Similar successional events, also involving Gammaproteobacteria, have been observed in nearshore systems as well.

Bioremediation of Atmospheric Hydrocarbons via Bacteria Naturally Associated with Leaves of Higher Plants

Bacteria associated with leaves of sixteen cultivated and wild plant species from all over Kuwait were analyzed by a culture-independent approach. This technique depended on partial sequencing of 16S rDNA regions in total genomic DNA from the bacterial consortia and comparing the resulting sequences with those in the GenBank database. To release bacterial cells from leaves, tough methods such as sonication co-released too much leaf chloroplasts whose DNA interfered with the bacterial DNA. A more satisfactory bacterial release with a minimum of chloroplast co-release was done by gently rubbing the leaf surfaces with soft tooth brushes in phosphate buffer. The leaves of all plant species harbored on their surfaces bacterial communities predominated by hydrocarbonoclastic (hydrocarbon-utilizing) bacterial genera. Leaves of 6 representative plants brought about in the laboratory effective removal of volatile hydrocarbons in sealed microcosms. Each individual plant species had a unique bacterial community structure. Collectively, the phyllospheric microflora on the studied plants comprised the genera Flavobacterium, Halomonas, Arthrobacter, Marinobacter, Neisseria, Ralstonia, Ochrobactrum. Exiguobacterium, Planomicrobium, Propionibacterium, Kocuria, Rhodococcus and Stenotrophomonas. This community structure was dramatically different from the structure we determined earlier for the same plants using the culture-dependent approach, although in both cases, hydrocarbonoclastic bacteria were frequent.

Biofilms constructed for the removal of hydrocarbon pollutants from hypersaline liquids

Hydrocarbonoclastic biofilms were established on sterile glass plates vertically submerged for 1 month in a hypersaline soil/water suspension containing 0.3% crude oil. The culture-dependent analysis of the microbial community in those biofilms revealed hydrocarbonoclastic species in the magnitude of 10(3) cells cm(-2). Those species belonged to the halophilic bacterial genera Marinobacter, Halomonas, Dietzia, Bacillus, Arhodomonas, Aeromonas and Kocuria as well as to the haloarchaeal genera Haloferax and Halobacterium. Those organisms were not evenly distributed over the biofilm surface area. The culture-independent analysis revealed a different community composition, which was based on four uncultured and four cultured taxa. Depending on the culture conditions and the sort of chemical amendments, the biofilms succeeded in removing in 2 weeks up to about 60-70% of crude oil, pure n-hexadecane and pure phenanthrene in hypersaline pond water samples. The amendment with KCl, MgSO4 and a vitamin mixture composed of thiamin, pyridoxine, vitamin B12, biotin, riboflavin and folic acid was most effective.

Emerging strategies and integrated systems microbiology technologies for biodiscovery of marine bioactive compounds

Marine microorganisms continue to be a source of structurally and biologically novel compounds with potential use in the biotechnology industry. The unique physiochemical properties of the marine environment (such as pH, pressure, temperature, osmolarity) and uncommon functional groups (such as isonitrile, dichloroimine, isocyanate, and halogenated functional groups) are frequently found in marine metabolites. These facts have resulted in the production of bioactive substances with different properties than those found in terrestrial habitats. In fact, the marine environment contains a relatively untapped reservoir of bioactivity. Recent advances in genomics, metagenomics, proteomics, combinatorial biosynthesis, synthetic biology, screening methods, expression systems, bioinformatics, and the ever increasing availability of sequenced genomes provides us with more opportunities than ever in the discovery of novel bioactive compounds and biocatalysts. The combination of these advanced techniques with traditional techniques, together with the use of dereplication strategies to eliminate known compounds, provides a powerful tool in the discovery of novel marine bioactive compounds. This review outlines and discusses the emerging strategies for the biodiscovery of these bioactive compounds.

Culture-dependent and culture-independent analysis of hydrocarbonoclastic microorganisms indigenous to hypersaline environments in Kuwait

The halophilic, hydrocarbonoclastic bacteria and archaea inhabiting two hypersaline coastal areas in Kuwait, one in the north and the other in the south, were counted and characterized. Environmental parameters in both areas were similar, with the exception of the soil organic carbon content, which was in the north higher than in the south. The hydrocarbonoclastic bacterial and haloarchaeal numbers and identities as analyzed using nutrient media of various salinities were similar in soil and pond water samples from both areas. The bacterial species recorded by this culture-dependent method belonged to the genera Halomonas, Chromohalobacter, Marinobacter, Exiguobacterium, Stenotrophomonas, Pseudomonas, Salinivibrio, and Bacillus. The haloarchaeal species belonged to the genera Haloferax and Halobacterium. When analyzed by fingerprinting of their amplified genomic DNA followed by sequencing of the electrophoresis-resolved bands, the same environmental samples revealed a different microbial composition. Bacterial phylotypes recorded by this culture-independent method were affiliated with the genera Ochrobactrum, Stenotrophomonas, Rhodococcus, and "Halomicrobium," whereas the archaeal phylotypes were affiliated with Halorussus, Halomicrobium, and Halorientalis. The observed diversity and composition similarity of the hydrocarbonocalastic microflora in both hypersaline areas suggest an effective potential for oil mineralization therein. This potential has been confirmed experimentally.

Enhanced bioremediation of oil-polluted, hypersaline, coastal areas in Kuwait via vitamin-fertilization

There is no research published sofar on managements that could bioremediate hypersaline soils and water polluted with hydrocarbons. The objective of this study was to assess the effect of vitamin amendment on hydrocarbon removal by microorganisms indigenous to such hypersaline environments. We used in this study ten hydrocarbonoclastic bacterial species and five archaeal species that had been isolated by the conventional plating method on media containing oil as a sole carbon source, from a hypersaline (3-4 M NaCl) coastal area in Kuwait, and characterized by sequencing of their 16S rRNA coding genes. The oil and pure hydrocarbon consumption was measured by gas-liquid chromatography. The oil and pure hydrocarbon consumption potential of all microorganisms in media with hypersalinity was enhanced by vitamin fertilization. This was true for individual microorganisms in pure cultures as well as for microbial consortia in hypersaline soil and water samples used as inocula. Most effective vitamins were thiamin, pyridoxine and vitamin B12. Vitamin fertilization using vitamin rich wastes or byproducts could be an effective practice for enhancing bioremediation of oil contaminated hypersaline environments.

Bias problems in culture-independent analysis of environmental bacterial communities: a representative study on hydrocarbonoclastic bacteria

Culture-dependent methods for bacterial community analysis are currently considered obsolete; therefore, molecular techniques are usually used instead. The results of the current study on hydrocarbonoclastic bacteria in various oily habitats in Kuwait showed however, that the bacterial identities varied dramatically according to the analytical approach used. For six desert and six seawater samples used in this study, the culture-independent and culture-dependent techniques each led to a unique bacterial composition. Problems related to the culture-dependent technique are well known. The results of the current study highlighted bias problems other than those already recorded in the literature for the molecular approaches. Thus, for example, in contrast to the culture-dependent technique, the primers used in the molecular approach preferentially amplified the 16S rDNAs of hydrocarbonoclastic bacteria in total genomic DNAs of all the studied environmental samples, and in addition, failed to reveal in any environmental sample members of the Actinobacteria. The primers used in the molecular approach also amplified certain “pure” 16S rDNAs, but failed to do so when these DNAs were in mixture. In view of these results, it is recommended that the two analytical approaches should be used simultaneously because their combined results would reflect the bacterial community composition more precisely than either of them can do alone.

Dominant petroleum hydrocarbon-degrading bacteria in the Archipelago Sea in South-West Finland (Baltic Sea) belong to different taxonomic groups than hydrocarbon degraders in the oceans

The natural petroleum hydrocarbon degrading capacity of the Archipelago Sea water in S-W Finland was studied in a microcosm experiment. Pristine and previously oil exposed sites were examined. Bacterial community fingerprinting was performed using terminal restriction fragment length polymorphism (T-RFLP) and samples from selected microcosms were sequenced. The abundance of PAH degradation genes was measured by quantitative PCR. Bacterial communities in diesel exposed microcosms diverged from control microcosms during the experiment. Gram positive PAH degradation genes dominated at both sites in situ, whereas gram negative PAH degrading genes became enriched in diesel microcosms. The dominant bacterial groups after a 14 days of diesel exposure were different depending on the sampling site, belonging to the class Actinobacteria (32%) at a pristine site and Betaproteobacteria (52%) at a previously oil exposed site. The hydrocarbon degrading bacteria in the Baltic Sea differ from those in the oceans, where most hydrocarbon degraders belong to Gammaproteobacteria.

Biofilm comprising phototrophic, diazotrophic, and hydrocarbon-utilizing bacteria: a promising consortium in the bioremediation of aquatic hydrocarbon pollutants

Biofilms harboring simultaneously anoxygenic and oxygenic phototrophic bacteria, diazotrophic bacteria, and hydrocarbon-utilizing bacteria were established on glass slides suspended in pristine and oily seawater. Via denaturing gradient gel electrophoresis analysis on PCR-amplified rRNA gene sequence fragments from the extracted DNA from biofilms, followed by band amplification, biofilm composition was determined. The biofilms contained anoxygenic phototrophs belonging to alphaproteobacteria; pico- and filamentous cyanobacteria (oxygenic phototrophs); two species of the diazotroph Azospirillum; and two hydrocarbon-utilizing gammaproteobacterial genera, Cycloclasticus and Oleibacter. The coexistence of all these microbial taxa with different physiologies in the biofilm makes the whole community nutritionally self-sufficient and adequately aerated, a condition quite suitable for the microbial biodegradation of aquatic pollutant hydrocarbons.

Oil-bioremediation potential of two hydrocarbonoclastic, diazotrophic Marinobacter strains from hypersaline areas along the Arabian Gulf coasts

Two halophilic, hydrocarbonoclastics bacteria, Marinobacter sedimentarum and M. flavimaris, with diazotrophic potential occured in hypersaline waters and soils in southern and northern coasts of Kuwait. Their numbers were in the magnitude of 10(3) colony forming units g(-1). The ambient salinity in the hypersaline environments was between 3.2 and 3.5 M NaCl. The partial 16S rRNA gene sequences of the two strains showed, respectively, 99 and 100% similarities to the sequences in the GenBank. The two strains failed to grow in the absence of NaCl, exhibited best growth and hydrocarbon biodegradation in the presence of 1 to 1.5 M NaCl, and still grew and maintained their hydrocarbonoclastic activity at salinities up to 5 M NaCl. Both species utilized Tween 80, a wide range of individual aliphatic hydrocarbons (C9-C40) and the aromatics benzene, biphenyl, phenanthrene, anthracene and naphthalene as sole sources of carbon and energy. Experimental evidence was provided for their nitrogen-fixation potential. The two halophilic Marinobacter strains successfully mineralized crude oil in nutrient media as well as in hypersaline soil and water microcosms without the use of any nitrogen fertilizers.

Plant-bacteria partnerships for the remediation of hydrocarbon contaminated soils

Plant-bacteria partnerships have been extensively studied and applied to improve crop yield. In addition to their application in agriculture, a promising field to exploit plant-bacteria partnerships is the remediation of soil and water polluted with hydrocarbons. Application of effective plant-bacteria partnerships for the remediation of hydrocarbons depend mainly on the presence and metabolic activities of plant associated rhizo- and endophytic bacteria possessing specific genes required for the degradation of hydrocarbon pollutants. Plants and their associated bacteria interact with each other whereby plant supplies the bacteria with a special carbon source that stimulates the bacteria to degrade organic contaminants in the soil. In return, plant associated-bacteria can support their host plant to overcome contaminated-induced stress responses, and improve plant growth and development. In addition, plants further get benefits from their associated-bacteria possessing hydrocarbon-degradation potential, leading to enhanced hydrocarbon mineralization and lowering of both phytotoxicity and evapotranspiration of volatile hydrocarbons. A better understanding of plant-bacteria partnerships could be exploited to enhance the remediation of hydrocarbon contaminated soils in conjunction with sustainable production of non-food crops for biomass and biofuel production.