Isolation of uncultivated anaerobic thermophiles from compost by supplementing cell extract of Geobacillus toebii in enrichment culture medium

Returning to Nature for the Next Generation of Antimicrobial Therapeutics

Antibiotics found in and inspired by nature are life-saving cures for bacterial infections and have enabled modern medicine. However, the rise in resistance necessitates the discovery and development of novel antibiotics and alternative treatment strategies to prevent the return to a pre-antibiotic era. Once again, nature can serve as a source for new therapies in the form of natural product antibiotics and microbiota-based therapies. Screening of soil bacteria, particularly actinomycetes, identified most of the antibiotics used in the clinic today, but the rediscovery of existing molecules prompted a shift away from natural product discovery. Next-generation sequencing technologies and bioinformatics advances have revealed the untapped metabolic potential harbored within the genomes of environmental microbes. In this review, we first highlight current strategies for mining this untapped chemical space, including approaches to activate silent biosynthetic gene clusters and in situ culturing methods. Next, we describe how using live microbes in microbiota-based therapies can simultaneously leverage many of the diverse antimicrobial mechanisms found in nature to treat disease and the impressive efficacy of fecal microbiome transplantation and bacterial consortia on infection. Nature-provided antibiotics are some of the most important drugs in human history, and new technologies and approaches show that nature will continue to offer valuable inspiration for the next generation of antibacterial therapeutics.

Shedding light on the composition of extreme microbial dark matter: alternative approaches for culturing extremophiles

More than 20,000 species of prokaryotes (less than 1% of the estimated number of Earth's microbial species) have been described thus far. However, the vast majority of microbes that inhabit extreme environments remain uncultured and this group is termed "microbial dark matter." Little is known regarding the ecological functions and biotechnological potential of these underexplored extremophiles, thus representing a vast untapped and uncharacterized biological resource. Advances in microbial cultivation approaches are key for a detailed and comprehensive characterization of the roles of these microbes in shaping the environment and, ultimately, for their biotechnological exploitation, such as for extremophile-derived bioproducts (extremozymes, secondary metabolites, CRISPR Cas systems, and pigments, among others), astrobiology, and space exploration. Additional efforts to enhance culturable diversity are required due to the challenges imposed by extreme culturing and plating conditions. In this review, we summarize methods and technologies used to recover the microbial diversity of extreme environments, while discussing the advantages and disadvantages associated with each of these approaches. Additionally, this review describes alternative culturing strategies to retrieve novel taxa with their unknown genes, metabolisms, and ecological roles, with the ultimate goal of increasing the yields of more efficient bio-based products. This review thus summarizes the strategies used to unveil the hidden diversity of the microbiome of extreme environments and discusses the directions for future studies of microbial dark matter and its potential applications in biotechnology and astrobiology.

Isolation and characterization of detergent-compatible amylase-, protease-, lipase-, and cellulase-producing bacteria

Detergent-compatible enzymes are the new trend followed by most in the detergent industry. Cellulases, lipases, proteases, and amylases are among the enzymes frequently used in detergents. Detergent-compatible enzymes can be obtained from many organisms, but the stability, cheapness, and availability of microbial enzymes make them preferable in industrial areas. In the present study, soil samples contaminated with household waste were collected from different regions of Trabzon (Turkey) for amylase-, cellulase-, protease-, and lipase-producing bacteria. A total of 55 bacterial isolates differing in colony morphology were purified from the samples and 25 of the isolates gave positive results in enzyme screening. The enzyme screening experiments revealed that 10 isolates produced amylase, 9 produced lipase, 7 produced cellulase, and 6 produced protease. While 2 isolates showed both protease and lipase activity, for 2 different isolates cellulose and amylase activity were detected together. It was also observed that one isolate, C37PLCA, produced all four enzymes. The morphological, physiological, and biochemical analyses of the bacteria from which we obtained the enzymes were performed and species close to them were determined using 16S rRNA sequences. Based on the results obtained, our enzymes show tremendous promise for the detergent industry.

Isolation and identification of marine microbial products

Background

The ocean is one of the world’s most important sources of bioactive chemicals in the marine environment. Microbiologists, ecologists, agronomists, taxonomists, and evolutionary biologists have been increasingly interested in marine microbial natural products (MMNPs) in recent decades.

Main body

Diverse marine bacteria appear to get the ability to manufacture an astounding diversity of MMNPs with a wide range of biological actions, including anti-tumor, antimicrobial, and anti-cardiovascular agents according to numerous studies.

Short conclusions

Innovative isolation and culture methodologies, tactics for identifying novel MMNPs via routine screens, metagenomics, genomics, combinatorial biosynthesis, and synthetic biology are all discussed in this review. There is also a discussion of potential issues and future directions for studying MMNPs.

Isolasi Bakteri Termofilik Sumber Air Panas Gedongsongo dengan Media Pengaya MB (Minimal Broth) dan TS (Taoge Sukrosa) serta Identifikasi Fenotip dan Genotip

Bakteri termofilik merupakan bakteri yang mampu bertahan hidup pada suhu tinggi di mana salah satu habitatnya adalah sumber air panas. Indonesia memiliki banyak sumber air panas yang potensial sebagai habitat bakteri termofilik. Dalam penelitian ini dilakukan isolasi bakteri termofilik sumber air panas gedongsongo dengan menggunakan pendekatan minimal media MB (Minimal Broth) dan TS (Taoge Sukosa) serta identifikasi fenotip dengan uji mikrobiologi yang meliputi pewarnaan gram dan morfologi dan identifikasi genotip dengan menggunakan urutan nukleotida gen 16S rRNA dan konstruksi pohon filogenetik dengan menggunakan program Phylip 3.68 ed. metode Distance matrix (Neighbour joining). Identifikasi enzim ekstraseluler secara kualitatif dilakukan dengan menggunakan media selektif yang meliputi uji selulase, uji a-amilase, uji protease dan uji P-galaktosidase. Dari penelitian diperoleh dua isolat tunggal bakteri termofilik yaitu isolat GS_MBan dan isolat GS_TSan. Isolat GS_MBan memiliki kemiripan dengan bakteri kelompok Anoxybacillus sp. sebesar 94-99%, berbentuk batang, bakteri gram positif, memiliki enzim ekstraseluler a-amilase, protease dan P-galaktosidase serta tidak menunjukkan potensi adanya enzim ekstraseluler selulase. Isolat GS_TSan memiliki kemiripan dengan bakteri kelompok Thermoanaerobacterium sp. sebesar 78-86%, berbentuk batang, bakteri gram negatif, memiliki enzim ekstraseluler a-amilase dan protease serta tidak menunjukkan potensi adanya enzim ekstraseluler P-galaktosidase dan selulase.

Plant powder teabags: a novel and practical approach to resolve culturability and diversity of rhizobacteria

We have developed teabags packed with dehydrated plant powders, without any supplements, for preparation of plant infusions necessary to develop media for culturing rhizobacteria. These bacteria are efficiently cultivated on such plant teabag culture media, with better progressive in situ recoverability compared to standard chemically synthetic culture media. Combining various plant-based culture media and incubation conditions enabled us to resolve unique denaturing gradient gel electrophoresis (DGGE) bands that were not resolved by tested standard culture media. Based on polymerase chain reaction PCR-DGGE of 16S rDNA fingerprints and sequencing, the plant teabag culture media supported higher diversity and significant increases in the richness of endo-rhizobacteria, namely Gammaproteobacteria (Enterobacteriaceae) and predominantly Alphaproteobacteria (Rhizobiaceae). This culminated in greater retrieval of the rhizobacteria taxa associated with the plant roots. We conclude that the plant teabag culture medium by itself, without any nutritional supplements, is sufficient and efficient for recovering and mirroring the complex and diverse communities of rhizobacteria. Our message to fellow microbial ecologists is: simply dehydrate your plant canopy, teabag it and soak it to prepare your culture media, with no need for any additional supplementary nutrients.

Exploration and isolation of novel thermophiles in frozen enrichment cultures derived from a terrestrial acidic hot spring

An isolation strategy, exploring novel microorganisms in frozen enrichment cultures (ENFE), which uses a combination of enrichment culture and 16S rRNA gene clone analysis, was evaluated for isolating uncultured thermophiles from a terrestrial acidic hot spring. The procedure comprised (a) multiple enrichment cultures under various conditions, (b) cryostorage of all enrichments, (c) microbial community analyses of the enrichments using 16S rRNA gene sequences, and (d) purification of microorganisms from enrichments containing previously uncultured microorganisms. The enrichments were performed under a total of 36 conditions, and 16 of these enrichments yielded positive microbial growth with the detection of three previously uncultured archaea. Two of the three previously uncultured archaea, strains HS-1 and HS-3, were successfully isolated. Strain HS-1 and HS-3 represented a novel lineage of the order Sulfolobales and novel species of the genus Sulfolobus, respectively. Although innovative isolation methods play strategic roles in isolating previously uncultured microorganisms, the ENFE strategy showed potential for characterizing and isolating such microorganisms using conventional media and techniques.

Synergism of glycoside hydrolase secretomes from two thermophilic bacteria cocultivated on lignocellulose

Two cellulolytic thermophilic bacterial strains, CS-3-2 and CS-4-4, were isolated from decayed cornstalk by the addition of growth-supporting factors to the medium. According to 16S rRNA gene-sequencing results, these strains belonged to the genus Clostridium and showed 98.87% and 98.86% identity with Clostridium stercorarium subsp. leptospartum ATCC 35414(T) and Clostridium cellulosi AS 1.1777(T), respectively. The endoglucanase and exoglucanase activities of strain CS-4-4 were approximately 3 to 5 times those of strain CS-3-2, whereas the β-glucosidase activity of strain CS-3-2 was 18 times higher than that of strain CS-4-4. The xylanase activity of strain CS-3-2 was 9 times that of strain CS-4-4, whereas the β-xylosidase activity of strain CS-4-4 was 27 times that of strain CS-3-2. The enzyme activities in spent cultures following cocultivation of the two strains with cornstalk as the substrate were much greater than those in pure cultures or an artificial mixture of samples, indicating synergism of glycoside hydrolase secretomes between the two strains. Quantitative measurement of the two strains in the cocultivation system indicated that strain CS-3-2 grew robustly during the initial stages, whereas strain CS-4-4 dominated the system in the late-exponential phase. Liquid chromatography-tandem mass spectrometry analysis of protein bands appearing in the native zymograms showed that ORF3880 and ORF3883 from strain CS-4-4 played key roles in the lignocellulose degradation process. Both these open reading frames (ORFs) exhibited endoglucanase and xylanase activities, but ORF3880 showed tighter adhesion to insoluble substrates at 4, 25, and 60°C owing to its five carbohydrate-binding modules (CBMs).

Recent advances in the discovery and development of marine microbial natural products

Marine microbial natural products (MMNPs) have attracted increasing attention from microbiologists, taxonomists, ecologists, agronomists, chemists and evolutionary biologists during the last few decades. Numerous studies have indicated that diverse marine microbes appear to have the capacity to produce an impressive array of MMNPs exhibiting a wide variety of biological activities such as antimicrobial, anti-tumor, anti-inflammatory and anti-cardiovascular agents. Marine microorganisms represent an underexplored reservoir for the discovery of MMNPs with unique scaffolds and for exploitation in the pharmaceutical and agricultural industries. This review focuses on MMNPs discovery and development over the past decades, including innovative isolation and culture methods, strategies for discovering novel MMNPs via routine screenings, metagenomics, genomics, combinatorial biosynthesis, and synthetic biology. The potential problems and future directions for exploring MMNPs are also discussed.

Phylogenetic analysis of the bacterial community in a full scale autothermal thermophilic aerobic digester (ATAD) treating mixed domestic wastewater sludge for land spread

The bacterial community associated with a full scale autothermal thermophilic aerobic digester (ATAD) treating sludge, originating from domestic wastewater and destined for land spread, was analysed using a number of molecular approaches optimised specifically for this high temperature environment. 16S rDNA genes were amplified directly from sludge with universally conserved and Bacteria-specific rDNA gene primers and a clone library constructed that corresponded to the late thermophilic stage (t = 23 h) of the ATAD process. Sequence analyses revealed various 16S rDNA gene sequence types reflective of high bacterial community diversity. Members of the bacterial community included α- and β-Proteobacteria, Actinobacteria with High G + C content and Gram-Positive bacteria with a prevalence of the Firmicutes (Low G + C) division (class Clostridia and Bacillus). Most of the ATAD clones showed affiliation with bacterial species previously isolated or detected in other elevated temperature environments, at alkaline pH, or in cellulose rich environments. Several phylotypes associated with Fe(III)- and Mn(IV)-reducing anaerobes were also detected. The presence of anaerobes was of interest in such large scale systems where sub-optimal aeration and mixing is often the norm while the presence of large amounts of capnophiles suggest the possibility of limited convection and entrapment of CO(2) within the sludge matrix during digestion. Comparative analysis with organism identified in other ATAD systems revealed significant differences based on optimised techniques. The abundance of thermophilic, alkalophilic and cellulose-degrading phylotypes suggests that these organisms are responsible for maintaining the elevated temperature at the later stages of the ATAD process.

A commensal symbiotic interrelationship for the growth of Symbiobacterium toebii with its partner bacterium, Geobacillus toebii

Background

Symbiobacterium toebii is a commensal symbiotic thermophile that absolutely requires its partner bacterium Geobacillus toebii for growth. Despite development of an independent cultivation method using cell-free extracts, the growth of Symbiobacterium remains unknown due to our poor understanding of the symbiotic relationship with its partner bacterium. Here, we investigated the interrelationship between these two bacteria for growth of S. toebii using different cell-free extracts of G. toebii.

Results

Symbiobacterium toebii growth-supporting factors were constitutively produced through almost all growth phases and under different oxygen tensions in G. toebii, indicating that the factor may be essential components for growth of G. toebii as well as S. toebii. The growing conditions of G. toebii under different oxygen tension dramatically affected to the initial growth of S. toebii and the retarded lag phase was completely shortened by reducing agent, L-cysteine indicating an evidence of commensal interaction of microaerobic and anaerobic bacterium S. toebii with a facultative aerobic bacterium G. toebii. In addition, the growth curve of S. toebii showed a dependency on the protein concentration of cell-free extracts of G. toebii, demonstrating that the G. toebii-derived factors have nutrient-like characters but not quorum-sensing characters.

Conclusions

Not only the consistent existence of the factor in G. toebii during all growth stages and under different oxygen tensions but also the concentration dependency of the factor for proliferation and optimal growth of S. toebii, suggests that an important biosynthetic machinery lacks in S. toebii during evolution. The commensal symbiotic bacterium, S. toebii uptakes certain ubiquitous and essential compound for its growth from environment or neighboring bacteria that shares the equivalent compounds. Moreover, G. toebii grown under aerobic condition shortened the lag phase of S. toebii under anaerobic and microaerobic conditions, suggests a possible commensal interaction that G. toebii scavengers ROS/RNS species and helps the initial growth of S. toebii.

Bacterial community in the personal-use composting reactor revealed by isolation and cultivation-independent method

Composting is an efficient and cost-effective process for organic waste treatment. In order to expand our knowledge regarding microorganisms and their roles in the composting process, bacterial community structures in the personal-use composting reactor were examined by isolation and 16S rDNA clone analysis (cultivation-independent method). The results of 16S rDNA clone analysis showed that populations of the Bacillaceae family (such as Bacillus spp., Cerasibacillus spp., Gracilibacillus spp.), dominate (98%). By using cultivation method, a total of four species including one novel species (Ureibacillus thermosphaericus, Geobacillus thermoglucosidasius, G. toebii and Thermobacillus composti) were isolated, and were classified into the order Bacillales corresponding to the result of 16S rDNA clone analysis. However, most species detected by clone analysis have not been cultivated, and may be viable but non-culturable VBNC species implying symbiotic interactions among the microorganisms.

Ohtaekwangia koreensis gen. nov., sp. nov. and Ohtaekwangia kribbensis sp. nov., isolated from marine sand, deep-branching members of the phylum Bacteroidetes

Two Gram-stain-negative, non-motile, non-spore-forming, rod-shaped bacterial strains, designated 3B-2(T) and 10AO(T), were isolated from a sand sample collected from the west coast of the Korean peninsula by using low-nutrient media, and their taxonomic positions were investigated in a polyphasic study. The strains did not grow on marine agar. They grew optimally at 30 °C and pH 6.5-7.5. Strains 3B-2(T) and 10AO(T) shared 97.5 % 16S rRNA gene sequence similarity and mean level of DNA-DNA relatedness of 12 %. In phylogenetic trees based on 16S rRNA gene sequences, strains 3B-2(T) and 10AO(T), together with several uncultured bacterial clones, formed independent lineages within the evolutionary radiation encompassed by the phylum Bacteroidetes. Strains 3B-2(T) and 10AO(T) contained MK-7 as the predominant menaquinone and iso-C(15 : 0) and C(16 : 1)ω5c as the major fatty acids. The DNA G+C contents of strains 3B-2(T) and 10AO(T) were 42.8 and 44.6 mol%, respectively. Strains 3B-2(T) and 10AO(T) exhibited very low levels of 16S rRNA gene sequence similarity (<85.0 %) to the type strains of recognized bacterial species. These data were sufficient to support the proposal that the novel strains should be differentiated from previously known genera of the phylum Bacteroidetes. On the basis of the data presented, we suggest that strains 3B-2(T) and 10AO(T) represent two distinct novel species of a new genus, for which the names Ohtaekwangia koreensis gen. nov., sp. nov. (the type species; type strain 3B-2(T)  = KCTC 23018(T)  = CCUG 58939(T)) and Ohtaekwangia kribbensis sp. nov. (type strain 10AO(T)  = KCTC 23019(T)  = CCUG 58938(T)) are proposed.

Strategies for culture of 'unculturable' bacteria

Molecular ecology methods are now well established for the culture-independent characterization of complex bacterial communities associated with various environmental and animal habitats and are revealing the extent of their diversity. By comparison, it has become clear that only a small minority of microorganisms are readily cultivated in vitro, with the majority of all bacteria remaining 'unculturable' using standard methods. Yet, it is only through the isolation of bacterial species in pure culture that they may be fully characterized, both for their physiological and pathological properties. Hence, the endeavour to devise novel cultivation methods for microorganisms that appear to be inherently resistant to artificial culture is a most important one. This minireview discusses the possible reasons for 'unculturability' and evaluates advances in the cultivation of previously unculturable bacteria from complex bacterial communities. Methods include the use of dilute nutrient media particularly suited for the growth of bacteria adapted to oligotrophic conditions, and the provision of simulated natural environmental conditions for bacterial culture. This has led to the recovery of 'unculturables' from soil and aquatic environments, likely to be due to the inclusion of essential nutrients and/or signalling molecules from the native environment.

Characterization of the depth-related changes in the microbial communities in Lake Hovsgol sediment by 16S rRNA gene-based approaches

The undisturbed sediment of Lake Hovsgol (Mongolia) is scientifically important because it represents a record of the environmental changes that took place between the Holocene (the present age) and Pleistocene (the last ice age; 12,000 14C years before present day). Here, we investigated how the current microbial communities change as the depth increases by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA genes of the microbial communities. The microbial diversity, as estimated by the Shannon index, decreased as the depth increased. In particular, significant changes in archaeal diversity were observed in the middle depth (at 39-42 cm depth of total 60 cm depth) that marks the border between the Holocene and Pleistocene. Phylotype belonging to Beta-and Gamma-Proteobacteria were the predominant bacteria and most of these persisted throughout the depth examined. However, as the depth increased, some bacteria (some genera belonging to Beta-Proteobacteria, Nitrospira, and OP8-9) were not detectable while others (some genera belonging to Alpha-, Beta-, Gamma-Proteobacteria) newly detected by DGGE. Crenarchaea were the predominant archaea and only one phylotype belonging to Euryarchaea was found. Both the archaeal and bacterial profiles revealed by the DGGE band patterns could be grouped into four and three subsets, respectively, subsets that were largely divided by the border between the Holocene and Pleistocene. Thus, the diversity of the current microbial communities in Lake Hovsgol sediments decreases with increasing depth. These changes probably relate to the environmental conditions in the sediments, which were shaped by the paleoclimatic events taking place between the Holocene and Pleistocene.