Cyanobacteria - a neglected component of biodiversity: patterns of species diversity in inland marshes of northern Belize (Central America)

Estimating taxonomic and functional structure along a tropical estuary: linking metabolic traits and aspects of ecosystem functioning

Microbial life forms are among the most ubiquitous on Earth, yet many remain understudied in Caribbean estuaries. We report on the prokaryote community composition of the Urabá Estuary in the Colombian Caribbean using 16S rRNA gene-transcript sequencing. We also assessed potential functional diversity through 38 metabolic traits inferred from 16S rRNA gene data. Water samples were collected from six sampling stations at two depths with contrasting light-penetration conditions along an approximately 100 km transect in the Gulf of Urabá in December 2019. Non-metric multidimensional scaling analysis grouped the samples into two distinct clusters along the transect and between depths. The primary variables influencing the prokaryote community composition were the sampling station, depth, salinity, and dissolved oxygen levels. Twenty percent of genera (i.e., 58 out 285) account for 95% of the differences between groups along the transect and among depths. All of the 38 metabolic traits studied showed some significant relationship with the tested environmental variables, especially salinity and except with temperature. Another non-metric multidimensional scaling analysis, based on community-weighted mean of traits, also grouped the samples in two clusters along the transect and over depth. Biodiversity facets, such as richness, evenness, and redundancy, indicated that environmental variations-stemming from river discharges-introduce an imbalance in functional diversity between surface prokaryote communities closer to the estuary's head and bottom communities closer to the ocean. Our research broadens the use of 16S rRNA gene transcripts beyond mere taxonomic assignments, furthering the field of trait-based prokaryote community ecology in transitional aquatic ecosystems.IMPORTANCEThe resilience of a dynamic ecosystem is directly tied to the ability of its microbes to navigate environmental gradients. This study delves into the changes in prokaryote community composition and functional diversity within the Urabá Estuary (Colombian Caribbean) for the first time. We integrate data from 16S rRNA gene transcripts (taxonomic and functional) with environmental variability to gain an understanding of this under-researched ecosystem using a multi-faceted macroecological framework. We found that significant shifts in prokaryote composition and in primary changes in functional diversity were influenced by physical-chemical fluctuations across the estuary's environmental gradient. Furthermore, we identified a potential disparity in functional diversity. Near-surface communities closer to the estuary's head exhibited differences compared to deeper communities situated farther away. Our research serves as a roadmap for posing new inquiries about the potential functional diversity of prokaryote communities in highly dynamic ecosystems, pushing forward the domain of multi-trait-based prokaryote community ecology.

Phylogenic diversity of bacteria associated with potentially toxic cyanobacteria Microcystis aeruginosa: a synthesis on its bloom dynamics

The occurrence of toxic bloom-forming cyanobacteria, Microcystis aeruginosa, has been frequently reported worldwide. These colony forming toxic cyanobacteria harbour a wide range of heterotrophic bacterial communities. The present study has attempted to understand the bloom dynamics of M. aeruginosa along with isolating their colony-associated culturable heterotrophic bacteria from two freshwater ponds in south India with a persisting cyanobacterial bloom. The monthly monitoring of these study areas revealed the conducive role of warm, stagnant waters with high nutrients in forming M. aeruginosa bloom. The peak values of temperature, nitrate, and phosphate at station 1 reached up to 30.5 °C, 4.48 mg/L, 1.64 mg/L, and at station 2, 31 °C, 3.45 mg/L, and 0.62 mg/L, respectively. Twenty-eight bacterial isolates belonging to Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Actinobacteria, and Firmicutes were obtained during the study. Among these 28 isolates, Firmicutes was dominant with the M. aeruginosa bloom from both the study areas.

Roholtiella volcanica sp. nov., a New Species of Cyanobacteria from Kamchatkan Volcanic Soils

During a study of biodiversity of cyanobacteria in Gorely volcano soils (Kamchatka Peninsula), a strain of heterocytous, a false branching cyanobacterium with gradually tapered filaments, was isolated. Prominent features of the strain were purplish-grey trichomes and firm, distinct multilayered sheaths. Based on the results obtained from the morphological, ecological, and phylogenetic analysis using the 16S rRNA and 16S–23S ITS region, 16S–23S ITS secondary structure analysis, comparison of flanking regions of BoxB and V3 helices, and the p-distance between the 16S–23S ITS region, we describe our strain K7 as a novel species of the genus Roholtiella with the name Roholtiella volcanica sp. nov., in accordance with the International Code of Nomenclature for algae, fungi, and plants. This work continues the rapid expansion of the description of new taxa of cyanobacteria, and particularly demonstrates a coming phase in cyanobacterial taxonomy in which the discovery of new species in recently described genera rapidly increases our understanding of the diversity in this phylum.

RNA-Seq Analysis on the Microbiota Associated with the White Shrimp (Litopenaeus vannamei) in Different Stages of Development

White leg shrimp (Litopenaeus vannamei) is a widely cultured species along the Pacific coast and is one of the most important crustaceans in world aquaculture. The microbiome composition of L. vannamei has been previously studied in different developmental stages, but there is limited information regarding the functional role of the microbiome during the development of L. vannamei. In this study the metatranscriptome in different developmental stages of L. vannamei (larvae, juvenile and adult) were generated using next generation sequencing techniques. The bacterial phyla found throughout all the stages of development belonged to the Proteobacteria, Firmicutes and Actinobacteria, these bacterial phyla are present in the digestive tract and are capable of producing several hydrolytic enzymes, which agrees with high representation of the primary metabolism and energy production, in both host and the microbiome. In this sense, functional changes were observed as the development progressed, in both host and the microbiome, in stages of larvae the most represented metabolic functions were associated with biomass production; while in juvenile and adult stages a higher proportion of metabolic functions associated to biotic and abiotic stress in L. vannamei and the microbiome were shown. This study provides evidence of the interaction of the microbiome with L. vannamei, and how the stage of development and the culture conditions of this species influences the gene expression and the microbiome composition, which suggests a complex metabolic network present throughout the life cycle of L. vannamei.

Algal Toxic Compounds and Their Aeroterrestrial, Airborne and other Extremophilic Producers with Attention to Soil and Plant Contamination: A Review

The review summarizes the available knowledge on toxins and their producers from rather disparate algal assemblages of aeroterrestrial, airborne and other versatile extreme environments (hot springs, deserts, ice, snow, caves, etc.) and on phycotoxins as contaminants of emergent concern in soil and plants. There is a growing body of evidence that algal toxins and their producers occur in all general types of extreme habitats, and cyanobacteria/cyanoprokaryotes dominate in most of them. Altogether, 55 toxigenic algal genera (47 cyanoprokaryotes) were enlisted, and our analysis showed that besides the “standard” toxins, routinely known from different waterbodies (microcystins, nodularins, anatoxins, saxitoxins, cylindrospermopsins, BMAA, etc.), they can produce some specific toxic compounds. Whether the toxic biomolecules are related with the harsh conditions on which algae have to thrive and what is their functional role may be answered by future studies. Therefore, we outline the gaps in knowledge and provide ideas for further research, considering, from one side, the health risk from phycotoxins on the background of the global warming and eutrophication and, from the other side, the current surge of interest which phycotoxins provoke due to their potential as novel compounds in medicine, pharmacy, cosmetics, bioremediation, agriculture and all aspects of biotechnological implications in human life.

Diversity of Myxobacteria-We Only See the Tip of the Iceberg

The discovery of new antibiotics is mandatory with regard to the increasing number of resistant pathogens. One approach is the search for new antibiotic producers in nature. Among actinomycetes, Bacillus species, and fungi, myxobacteria have been a rich source for bioactive secondary metabolites for decades. To date, about 600 substances could be described, many of them with antibacterial, antifungal, or cytostatic activity. But, recent cultivation-independent studies on marine, terrestrial, or uncommon habitats unequivocally demonstrate that the number of uncultured myxobacteria is much higher than would be expected from the number of cultivated strains. Although several highly promising myxobacterial taxa have been identified recently, this so-called Great Plate Count Anomaly must be overcome to get broader access to new secondary metabolite producers. In the last years it turned out that especially new species, genera, and families of myxobacteria are promising sources for new bioactive metabolites. Therefore, the cultivation of the hitherto uncultivable ones is our biggest challenge.

Cephalothrix gen. nov. (Cyanobacteria): towards an intraspecific phylogenetic evaluation by multilocus analyses

For more than a decade, the taxonomy of the Phormidiaceae has been problematic, since morphologically similar organisms represent phylogenetically distinct entities. Based on 16S rRNA gene sequence analyses, the polyphyletic genus Phormidium and other gas-vacuolated oscillatorioids appear scattered throughout the cyanobacterial tree of life. Recently, several studies have focused on understanding the oscillatorioid taxa at the generic level. At the specific level, few studies have characterized cyanobacterial strains using combined datasets (morphology, ultrastructure and molecular multilocus analyses). Using a multifaceted approach, we propose a new, well-defined genus, Cephalothrix gen. nov., by analysing seven filamentous strains that are morphologically ‘intermediate’ between gas-vacuolated taxa and Phormidium. Furthermore, we characterize two novel species: Cephalothrix komarekiana sp. nov. (strains CCIBt 3277, CCIBt 3279, CCIBt 3523, CCALA 155, SAG 75.79 and UTEX 1580) and Cephalothrix lacustris sp. nov. (strain CCIBt 3261). The generic name and specific epithets are proposed under the provisions of the International Code of Nomenclature for Algae, Fungi, and Plants.

Polyphasic characterization of benthic cyanobacterial diversity from biofilms of the Guadarrama river (Spain): morphological, molecular, and ecological approaches(1)

The occurrence and environmental factors responsible for the distribution of benthic cyanobacteria in running waters remain largely unexplored in comparison with those of other aquatic ecosystems. In this study, combined data of ecological characteristics, molecular analysis (based on 16S rRNA gene), and direct microscopic inspection of environmental samples were analyzed in parallel with the morphological characterization of the isolated strains to investigate benthic cyanobacterial diversity in the Guadarrama river (Spain). A total of 17 species were identified that belonged to the genera Aphanocapsa, Pleurocapsa, Chroococcus, Chamaesiphon, Cyanobium, Pseudan-abaena, Leptolyngbya, Phormidium, Nostoc, and Tolypothrix. Phenotypic features were associated with the results of 16S rRNA gene sequencing, complementing existing morphological and genetic databases. A decrease in the cyanobacterial diversity was observed along a pollution gradient in the river. Water quality differed among the sampling sites, and variation in nutrient content was the principal difference among locations. These characteristics were closely associated with an upstream-downstream eutrophic gradient. Canonical correspondence analysis distinguished three groups of species with respect to the eutrophication gradient. The first group (Tolypothrix cf. tenuis, Nostoc punctiforme, Nostoc piscinale, Chamaesiphon investiens, Chroococcus minor, Leptolyngbya nostocorum, and Leptolyngbya tenuis) was characteristic of waters with low levels of nutrients. The second group (Cyanobium sp., Chamaesiphon polymorphus, Leptolyngbya boryana, Phormidium autumnale, Phormidium sp., and Aphanocapsa cf. rivularis) was characteristic of polluted waters, its members appearing mainly in great abundance under eutrophic-hypertrophic conditions. The third group of species (Pseudanabaena catenata, Aphanocapsa muscicola, and Nostoc carneum) was present at upstream and downstream sites.

Can amino acid carbon isotope ratios distinguish primary producers in a mangrove ecosystem?

RATIONALE

The relative contribution of carbon from terrestrial vs. marine primary producers to mangrove-based food webs can be challenging to resolve with bulk carbon isotope ratios (δ(13)C). In this study we explore whether patterns of δ(13)C values among amino acids (AAs) can provide an additional tool for resolving terrestrial and marine origins of carbon.

METHODS

Amino acid carbon isotope ratios (δ(13)C(AA)) were measured for several terrestrial and marine primary producers in a mangrove ecosystem at Spanish Lookout Caye (SLC), Belize, using gas chromatography-combustion-isotope ratio mass spectrometry. The δ(13)C values of essential amino acids (δ(13)C(EAA)) were measured to determine whether they could be used to differentiate terrestrial and marine producers using linear discriminant analysis.

RESULTS

Marine and terrestrial producers had distinct patterns of δ(13)C(EAA) values in addition to their differences in bulk δ(13)C values. Microbial mat samples and consumers (Crassostrea rhizophorae, Aratus pisonii, Littoraria sp., Lutjanus griseus) were most similar to marine producers. Patterns of δ(13)C(EAA) values for terrestrial producers were very similar to those described for other terrestrial plants.

CONCLUSIONS

The findings suggest that δ(13)C(EAA) values may provide another tool for estimating the contribution of terrestrial and marine sources to detrital foodwebs. Preliminary analyses of consumers indicate significant use of aquatic resources, consistent with other studies of mangrove foodwebs.

Natural hybridization in tropical spikerushes of Eleocharis subgenus Limnochloa (Cyperaceae): Evidence from morphology and DNA markers

PREMISE OF THE STUDY

Natural hybridization represents an important force driving plant evolution and affecting community structure and functioning. Hybridization may be overlooked, however, among morphologically highly uniform congeners. An excellent example of such a group is Eleocharis subgenus Limnochloa, which has no reliably proven hybrids. Does this reflect biological barriers to interspecific crosses or difficulties in detecting the hybrids? We tested the hypothesis that hybridization occurs among sympatric Eleocharis cellulosa, E. interstincta, and E. mutata in northern Belize, Central America. •

METHODS

Morphometric study (407 plants) was followed by examination of inter-simple sequence repeat (ISSR) polymorphisms (44 plants) and ITS sequence variation (33 plants). •

KEY RESULTS

Two putatively hybrid morphotypes were discerned-E. cellulosa-resembling and E. interstincta-resembling. DNA markers of E. cellulosa and E. interstincta displayed additive constitution in plants from one E. cellulosa-resembling population only. The other putatively hybrid populations contained ISSR and ITS markers of the species they resembled morphologically, several unique ISSR markers, and ITS sequences of an undescribed South American Limnochloa entity. DNA markers of E. mutata were absent in the putative hybrids. •

CONCLUSIONS

Simultaneous use of various types of molecular markers can overcome many pitfalls of investigations concerning hybridization among closely related and morphologically similar species. Northern Belize represents a hybrid zone of E. cellulosa and E. interstincta. A third participant in the hybridization events occurring in this zone is an unknown Limnochloa lineage but is not E. mutata. Interspecific hybridization may play a significant role in the diversification of Eleocharis.

Molecular characterization and the effect of salinity on cyanobacterial diversity in the rice fields of Eastern Uttar Pradesh, India

Background

Salinity is known to affect almost half of the world's irrigated lands, especially rice fields. Furthermore, cyanobacteria, one of the critical inhabitants of rice fields have been characterized at molecular level from many different geographical locations. This study, for the first time, has examined the molecular diversity of cyanobacteria inhabiting Indian rice fields which experience various levels of salinity.

Results

Ten physicochemical parameters were analyzed for samples collected from twenty experimental sites. Electrical conductivity data were used to classify the soils and to investigate relationship between soil salinity and cyanobacterial diversity. The cyanobacterial communities were analyzed using semi-nested 16S rRNA gene PCR and denaturing gradient gel electrophoresis. Out of 51 DGGE bands selected for sequencing only 31 which showed difference in sequences were subjected to further analysis. BLAST analysis revealed highest similarity for twenty nine of the sequences with cyanobacteria, and the other two to plant plastids. Clusters obtained based on morphological and molecular attributes of cyanobacteria were correlated to soil salinity. Among six different clades, clades 1, 2, 4 and 6 contained cyanobacteria inhabiting normal or low saline (having EC < 4.0 ds m^-1) to (high) saline soils (having EC > 4.0 ds m^-1), however, clade 5 represented the cyanobacteria inhabiting only saline soils. Whilst, clade 3 contained cyanobacteria from normal soils. The presence of DGGE band corresponding to Aulosira strains were present in large number of soil indicating its wide distribution over a range of salinities, as were Nostoc, Anabaena, and Hapalosiphon although to a lesser extent in the sites studied.

Conclusion

Low salinity favored the presence of heterocystous cyanobacteria, while very high salinity mainly supported the growth of non-heterocystous genera. High nitrogen content in the low salt soils is proposed to be a result of reduced ammonia volatilization compared to the high salt soils. Although many environmental factors could potentially determine the microbial community present in these multidimensional ecosystems, changes in the diversity of cyanobacteria in rice fields was correlated to salinity.

Biogeography: an emerging cornerstone for understanding prokaryotic diversity, ecology, and evolution

New questions about microbial ecology and diversity combined with significant improvement in the resolving power of molecular tools have helped the reemergence of the field of prokaryotic biogeography. Here, we show that biogeography may constitute a cornerstone approach to study diversity patterns at different taxonomic levels in the prokaryotic world. Fundamental processes leading to the formation of biogeographic patterns are examined in an evolutionary and ecological context. Based on different evolutionary scenarios, biogeographic patterns are thus posited to consist of dramatic range expansion or regression events that would be the results of evolutionary and ecological forces at play at the genotype level. The deterministic or random nature of those underlying processes is, however, questioned in light of recent surveys. Such scenarios led us to predict the existence of particular genes whose presence or polymorphism would be associated with cosmopolitan taxa. Furthermore, several conceptual and methodological pitfalls that could hamper future developments of the field are identified, and future approaches and new lines of investigation are suggested.