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Rare and unknown actinobacteria from unexplored environments have the potential to produce new bioactive molecules. This study aimed to use 16 s rRNA metabarcoding to determine the composition of the actinobacterial community, particularly focusing on rare and undescribed species, in a nature reserve within the Brazilian Cerrado called Sete Cidades National Park. Since this is an inaccessible area without due legal authorization, it is understudied, and, therefore, its diversity and biotechnological potential are not yet fully understood, and it may harbor species with groundbreaking genetic potential. In total, 543 operational taxonomic units (OTUs) across 14 phyla were detected, with Actinobacteria (41.2%), Proteobacteria (26.5%), and Acidobacteria (14.3%) being the most abundant. Within Actinobacteria, 107 OTUs were found, primarily from the families Mycobacteriaceae, Pseudonocardiaceae, and Streptomycetaceae. Mycobacterium and Streptomyces were the predominant genera across all samples. Seventeen rare OTUs with relative abundance < 0.1% were identified, with 82.3% found in only one sample yet 25.5% detected in all units. Notable rare and transient genera included Salinibacterium, Nocardia, Actinomycetospora_01, Saccharopolyspora, Sporichthya, and Nonomuraea. The high diversity and distribution of Actinobacteria OTUs indicate the area's potential for discovering new rare species. Intensified prospection on underexplored environments and characterization of their actinobacterial diversity could lead to the discovery of new species capable of generating innovative natural products.

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Lichens are not only fungal-algal symbiotic associations but also matrices for association with bacteria, and the bacterial diversity linked to lichens has been receiving more attention in studies. This study compares the diversity and possible metabolism of lichen-associated bacteria from saxicolous foliose and fruticose taxa Alectoria, Canoparmelia, Crocodia, Menegazzia, Usnea, and Xanthoparmelia from the Venezuelan Guiana Shield and the South African Highveld Plateau. We used DNA extractions from the lichen thalli to amplify the eukaryotic 18S rRNA gene (rDNA) and the V3-V4 region of the bacterial 16S rDNA, of which amplicons were then Sanger- and MiSeq-sequenced, respectively. The V3-V4 sequences of the associated bacteria were grouped into operational taxonomic units (OTUs) ascribed to twelve bacterial phyla previously found in the rock tripe Umbilicaria lichens. The bacterial OTUs emphasized the uniqueness of each region, while, at the species and higher ranks, the regional microbiomes were shown to be somewhat similar. Nevertheless, regional biomarker OTUs were screened to predict relevant metabolic pathways, which implicated different regional metabolic features.

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BACKGROUND: Artisanal and small-scale gold mining activities are producing contamination with heavy metals and metalloids (HMM) into soils and water worldwide. The HMM are considered as one of the major abiotic stresses due to their long-term persistence in soil. In this context, arbuscular mycorrhizal fungi (AMF) confer resistance to a variety of abiotic plant stressors including HMM. However, little is known regarding the diversity and composition of AMF communities in heavy metal polluted sites in Ecuador. METHODS: In order to investigate the AMF diversity, root samples and associated soil of six plant species were collected from two sites polluted by heavy metals, located in Zamora-Chinchipe province, Ecuador. The AMF 18S nrDNA genetic region was analyzed and sequenced, and fungal OTUs were defined based on 99% sequence similarity. Results were contrasted with AMF communities from a natural forest and from reforestation sites located in the same province and with available sequences in GenBank. RESULTS: The main pollutants in soils were Pb, Zn, Hg, Cd and Cu with concentrations exceeding the soil reference value for agricultural use. Molecular phylogeny and OTU delimitation showed 19 OTUs, the family Glomeraceae was the most OTU-rich followed by Archaeosporaceae, Acaulosporaceae, Ambisporaceae and Paraglomeraceae. Most of the OTUs (11 of 19) have been found at other locations worldwide, 14 OTUs were proven from nearby non-contaminated sites in Zamora-Chinchipe. CONCLUSION: Our study showed that there are no specialized OTUs at the studied HMM polluted sites, but rather generalists adapted to a wide variety of habitats. Their potential role in phytoremediation approaches remains to be investigated.

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Gut microbiota are influenced by factors such as diet, habitat, and social contact, which directly affect the host's health. Studies related to gut microbiota in non-human primates are increasing worldwide. However, little remains known about the gut bacterial composition in wild Brazilian monkeys. Therefore, we studied the fecal microbiota composition of wild black capuchin monkey (Sapajus nigritus) (n=10) populations from two different Atlantic Forest biome fragments (five individuals per fragment) in south Brazil. The bacterial community was identified via the high-throughput sequencing and partial amplification of the 16S rRNA gene (V4 region) using an Ion Personal Genome Machine (PGMTM) System. In contrast to other studies involving monkey microbiota, which have generally reported the phyla Firmicutes and Bacteroidetes as predominant, black capuchin monkeys showed a high relative abundance of Proteobacteria ( χ ¯ = 80.54%), followed by Firmicutes ( χ ¯ = 12.14%), Actinobacteria ( χ ¯ = 4.60%), and Bacteriodetes ( χ ¯ = 1.31%). This observed particularity may have been influenced by anthropogenic actions related to the wild habitat and/or diet specific to the Brazilian biome's characteristics and/or monkey foraging behavior. Comparisons of species richness (Chao1) and diversity indices (Simpson and InvSimpson) showed no significant differences between the two groups of monkeys. Interestingly, PICRUSt2 analysis revealed that metabolic pathways present in the bacterial communities were associated with xenobiotic biodegradation and the biosynthesis of secondary metabolites, which may suggest positive effects on monkey health and conservation in this anthropogenic habitat. Infectious disease-associated microorganisms were also observed in the samples. The present study provides information about the bacterial population and metabolic functions present in fecal microbiota, which may contribute to a better understanding of the ecology and biology of black capuchin monkeys living in forest fragments within the Atlantic Forest biome in southern Brazil. Additionally, the present study demonstrates that the fecal bacterial communities of wild black capuchin monkeys in this area are divergent from those of other wild non-human primates.

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The interplay between shrimp immune system, its environment, and microbiota contributes to the organism's homeostasis and optimal production. The metagenomic composition is typically studied using 16S rDNA profiling by clustering amplicon sequences into operational taxonomic units (OTUs) and, more recently, amplicon sequence variants (ASVs). Establish the compatibility of the taxonomy, α, and ß diversity described by both methods is necessary to compare past and future shrimp microbiota studies. Here, we used identical sequences to survey the V3 16S hypervariable-region using 97% and 99% OTUs and ASVs to assess the hepatopancreas and intestine microbiota of L. vannamei from two ponds under standardized rearing conditions. We found that applying filters to retain clusters >0.1% of the total abundance per sample enabled a consistent taxonomy comparison while preserving >94% of the total reads. The three sets turned comparable at the family level, whereas the 97% identity OTU set produced divergent genus and species profiles. Interestingly, the detection of organ and pond variations was robust to the clustering method's choice, producing comparable α and ß-diversity profiles. For comparisons on shrimp microbiota between past and future studies, we strongly recommend that ASVs be compared at the family level to 97% identity OTUs or use 99% identity OTUs, both using tailored frequency filters.

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The goal of the study was to characterize the intestinal tract bacterial microbiota composition of Penaeus vannamei in intensive commercial ponds in Ecuador, comparing two shrimp-farming phases: nursery and harvest. Bacterial microbiota was examined by sequencing amplicons V2-V3 of the 16S rRNA using Ion Torrent technology. Archaea sequences were detected in both phases. Sequence analyses revealed quantitative and qualitative differences between the nursery phase and the harvest phase in shrimp intestinal microbiota composition. The main differences were observed at the phylum level during the nursery phase, and the prevailing phyla were CKC4 (37.3%), Proteobacteria (29.8%), Actinobacteria (11.6%), and Firmicutes (10.1%). In the harvest phase, the prevailing phyla were Proteobacteria (28.4%), Chloroflexi (19.9%), and Actinobacteria (15.1%). At the genus level, microbiota from the nursery phase showed greater relative abundances of CKC4 uncultured bacterium (37%) and Escherichia-Shigella (18%). On the contrary, in the microbiota of harvested shrimp, the prevailing genera were uncultured Caldilinea (19%) and Alphaproteobacteria with no other assigned rate (10%). The analysis of similarity ANOSIM test (beta diversity) indicated significant differences between the shrimp microbiota for these two farming phases. Similarly, alfa-diversity analysis (Chao1) indicated that the microbiota at harvest was far more diverse than the microbiota during the nursery phase, which showed a homogeneous composition. These results suggest that shrimp microbiota diversify their composition during intensive farming. The present work offers the most detailed description of the microbiota of P. vannamei under commercial production conditions to date.

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Adaptive radiations provide unique opportunities to test whether and how recent ecological and evolutionary diversification of host species structures the composition of entire bacterial communities. We used 16S rRNA gene sequencing of faecal samples to test for differences in the gut microbiota of six species of Puerto Rican Anolis lizards characterized by the evolution of distinct 'ecomorphs' related to differences in habitat use. We found substantial variation in the composition of the microbiota within each species and ecomorph (trunk-crown, trunk-ground, grass-bush), but no differences in bacterial alpha diversity among species or ecomorphs. Beta diversity analyses revealed subtle but significant differences in bacterial composition related to host phylogeny and species, but these differences were not consistently associated with Anolis ecomorph. Comparison of a trunk-ground species from this clade (A. cristatellus) with a distantly related member of the same ecomorph class (A. sagrei) where the two species have been introduced and are now sympatric in Florida revealed pronounced differences in the alpha diversity and beta diversity of their microbiota despite their ecological similarity. Comparisons of these populations with allopatric conspecifics also revealed geographic differences in bacterial alpha diversity and beta diversity within each species. Finally, we observed high intraindividual variation over time and strong effects of a simplified laboratory diet on the microbiota of A. sagrei. Collectively, our results indicate that bacterial communities are only weakly shaped by the diversification of their lizard hosts due to the strikingly high levels of bacterial diversity and variation observed within Anolis species.

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