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Over the past decade, an increasing number of studies have emphasized the importance of the host microbiome in influencing organismal health and development. Aligned with this understanding, our study aimed to investigate the potential association between the turbot (Scophthalmus maximus) phenotypic traits and the post-larval bacteriome. Turbot post-larvae were sampled from twenty randomly selected production cycles thirty days after hatching (DAH) across multiple post-larval production batches over a three-month period (April to June). Fish were selectively sampled based on five phenotypic traits, namely, normal, large, small, malformed, and depigmented. Our results showed that small-sized post-larvae had significantly higher bacterial phylogenetic diversity in their bacterial communities than all other phenotypes. A more in-depth compositional analysis also revealed specific associations between certain bacterial taxa and fish phenotypes. For example, the genera Aliivibrio and Sulfitobacter were enriched in small-sized post-larvae, while the family Micrococcaceae were predominantly found in larger post-larvae. Furthermore, genus Exiguobacterium was linked to depigmented larvae, and genus Pantoea was more prevalent in normal post-larvae. These observations underscore the importance of further research to understand the roles of these bacterial taxa in larval growth and phenotypic differentiation. Such insights could contribute to developing microbiome modulation strategies, which may enhance turbot post-larval health and quality and improve larviculture production. [ABSTRACT FROM AUTHOR]

Climate change may increase the vulnerability of aquifers to contamination through extreme precipitation and extended drought periods. Therefore, the understanding of groundwater ecosystem dynamics is crucial, with bacterial assemblages playing a major role in biogeochemical cycles. The present research describes a geospatial study targeting the bacterial community structure of groundwaters from the largest karst aquifer in Portugal (the Maciço Calcário Estremenho), integrating hydrogeochemical and bacterial diversity data. A total of 22 samples were analyzed from a set of 11 geographically sparsely distributed groundwater sources in dry vs. wet seasons. The 16S rRNA gene barcoding data revealed bacterial community variability across samples in space and time. The phylum Proteobacteria was dominant across all samples (from 44 to 92% of total sequence reads), mainly represented by the classes Alphaproteobacteria (orders Sphingomonadales, BD7–3, Rhizobiales and Rhodospirillales), Betaproteobacteria (orders Burkholderiales, Rhodocyclales, Nitrosomonadales), Gammaproteobacteria (orders Pseudomonadales, Xanthomonadales, Alteromonadales, Legionellales) and Deltaproteobacteria (orders Myxococcales, Spirobacillales). Variation in the bacterial community was primarily attributed to parameters such as redox conditions (DO, ORP), Fe, Mn, SO4, PO4, Sr and Cl, but also some minor and trace elements (Al, V, Cr, Cu, Pb). Our results provide novel insights into bacterial diversity in relation to groundwater hydrogeochemistry. The strong dominance of OTUs related to bacterial taxa associated with nitrification/denitrification also highlights a potentially important role of these assemblages on nutrients (nitrogen sources) and groundwater quality dynamics at this karstic aquifer system. Moreover, the integration of bacterial assemblages information is emphasized as central for water quality monitoring programs. [ABSTRACT FROM AUTHOR]

Marine microbiomes are prolific sources of bioactive natural products of potential pharmaceutical value. This study inspected two culture collections comprising 919 host-associated marine bacteria belonging to 55 genera and several thus-far unclassified lineages to identify isolates with potentially rich secondary metabolism and antimicrobial activities. Seventy representative isolates had their genomes mined for secondary metabolite biosynthetic gene clusters (SM-BGCs) and were screened for antimicrobial activities against four pathogenic bacteria and five pathogenic Candida strains. In total, 466 SM-BGCs were identified, with antimicrobial peptide- and polyketide synthase-related SM-BGCs being frequently detected. Only 38 SM-BGCs had similarities greater than 70% to SM-BGCs encoding known compounds, highlighting the potential biosynthetic novelty encoded by these genomes. Cross-streak assays showed that 33 of the 70 genome-sequenced isolates were active against at least one Candida species, while 44 isolates showed activity against at least one bacterial pathogen. Taxon-specific differences in antimicrobial activity among isolates suggested distinct molecules involved in antagonism against bacterial versus Candida pathogens. The here reported culture collections and genome-sequenced isolates constitute a valuable resource of understudied marine bacteria displaying antimicrobial activities and potential for the biosynthesis of novel secondary metabolites, holding promise for a future sustainable production of marine drug leads. [ABSTRACT FROM AUTHOR]

Climate change is enhancing the frequency of cyanobacterial blooms not only during summer but also in spring and autumn, leading to increased ecological impacts. The bacterioplankton community composition (BCC), in particular, is deeply affected by these blooms, although at the same time BCC can also play important roles in blooms' dynamics. However, more information is still needed regarding BCC during species-specific cyanobacterial blooms. The goal of this study was to assess BCC succession in a hypereutrophic shallow lake (Vela Lake, Portugal) during a warm spring using a metagenomic approach to provide a glimpse of the changes these communities experience during the dominance of Aphanizomenon-like bloom-forming species. BCC shifts were studied using 16S rRNA gene metabarcoding and multivariate analyses. A total of 875 operational taxonomic units (OTUs) were retrieved from samples. In early spring, the dominant taxa belonged to Proteobacteria (mainly Alphaproteobacteria—Rickettsiales) and Bacteroidetes (Saprospirales, Flavobacteriales and Sphingobacteriales). However, at the end of May, a bloom co-dominated by cyanobacterial populations of Aphanizomenon gracile, Sphaerospermopsis aphanizomenoides and Synechococcus sp. developed and persisted until the end of spring. This led to a major BCC shift favouring the prevalence of Alphaproteobacteria (Rickettsiales and also Rhizobiales, Caulobacteriales and Rhodospirillales) and Bacteroidetes (Saprospirales, followed by Flavobacteriales and Sphingobacteriales). These results contribute to the knowledge of BCC dynamics during species-specific cyanobacterial blooms, showing that BCC is strongly affected (directly or indirectly) by Aphanizomenon-Sphaerospermopsis blooms. [ABSTRACT FROM AUTHOR]