Biology subjects

Sanz-Saez, I.

Publications and source records attributed to Sanz-Saez, I..

3 recordsLinked to original sources

bioRxiv2022

Abundant deep ocean heterotrophic bacteria are culturable

Traditional culture techniques usually retrieve only a small fraction of the environmental marine microbial diversity, which mainly belong to the so-called rare biosphere. However, this paradigm has not been fully tested at a broad scale, especially in the deep ocean. Here, we examined the fraction of heterotrophic bacterial communities in photic and deep ocean layers that could be recovered by culture-dependent techniques at a large scale. We compared 16S rRNA gene sequences from a collection of 2003 cultured isolates of heterotrophic marine bacteria with global 16S rRNA metabarcoding datasets (16S TAGs) covering surface, mesopelagic and bathypelagic ocean samples that included 16 of the 22 samples used for isolation. These global datasets represent 60,322 unique 16S amplicon sequence variants (ASVs). Our results reveal a significantly higher proportion of isolates identical to ASVs in deeper ocean layers reaching up to a 28% of the 16S TAGs of the bathypelagic microbial communities, which included the isolation of 3 of the top 10 most abundant 16S ASVs in the global bathypelagic ocean, related to the genera Sulfitobacter, Halomonas and Erythrobacter. These cultured isolates contributed differently to the prokaryotic communities across different plankton size fractions, recruiting between 38% in the free-living size fraction (0.2-0.8 m) and up to 45% in the largest plankton size fraction (20-200 m) in the bathypelagic ocean. Our findings support the hypothesis that sinking particles in the bathypelagic realm act as resource-rich habitats, suitable for the growth of heterotrophic bacteria with a copiotroph lifestyle that can be cultured, and that these cultivable bacteria can also thrive as free-living bacteria.

ecology↗

bioRxiv2021

Prevalence of heterotrophic methylmercury detoxifying bacteria across oceanic regions

Microbial reduction of inorganic divalent mercury (Hg2+) and methylmercury (MeHg) demethylation is performed by the mer operon, specifically by merA and merB genes respectively, but little is known about the mercury tolerance capacity of marine microorganisms and its prevalence in the global ocean. Here, we explored the distribution of these genes in 290 marine heterotrophic bacteria (Alteromonas and Marinobacter spp.) isolated from different oceanographic regions and depths, and assessed their tolerance to diverse concentrations of Hg2+ and MeHg. About 25% of the isolates presented merA and only 8.9% presented both merAB genes, including the strain ISS312 that exhibited the highest tolerance capacity and a degradation efficiency of 98.2% in 24 h. Fragment recruitment analyses of ISS312 genome against microbial metagenomes indicated an extensive distribution across the global bathypelagic ocean. Our findings highlighted that mercury resistance genes are widely distributed in a non-highly polluted environment such as the pelagic marine environment, and that degradation of the neurotoxic MeHg can be performed through the ocean water column by some heterotrophic bacteria at high efficiency with important implications in the biogeochemical cycle of mercury and potentially for the environment and human health. TeaserActive mercury resistance genes detected in marine cultured bacteria are widely distributed in the ocean including the bathypelagic zone.

microbiology↗

bioRxiv2019

Diversity patterns of marine heterotrophic culturable bacteria along vertical and latitudinal gradients

Nowadays, there is a significant gap in the knowledge of the diversity and patterns for marine heterotrophic culturable microorganisms. In addition, most of the bacterial isolation efforts have focused on the photic ocean leaving the deep ocean less explored. We have isolated 1561 bacterial strains covering both photic (817) and aphotic layers (744) including isolates from the oxygen minimum zone (362) and the bathypelagic (382) from a variety of oceanographic regions including the North Western Mediterranean Sea, the North and South Atlantic Oceans, the Indian, the Pacific, and the Arctic Oceans. The partial sequencing of the 16S rRNA gene of all isolates revealed that they mainly affiliate with the classes Alphaproteobacteria (35.9%) and Gammaproteobacteria (38.6%), as well as, phylum Bacteroidetes (16.5%). The genera Alteromonas and Erythrobacter were the most widespread heterotrophic bacteria in the ocean able to grow on solid agar media. When comparing the sequences of all isolates, 37% of them were 100% identical. In fact, we found that 59% of the total aphotic isolates were 100% identical to photic isolates, indicating the ubiquity of some bacterial isolates along the water column. Unweighted UniFrac distances did not show significant differences among stations regardless of their geographic distance or depth, reflecting the wide dispersion of the culturable bacterial assemblage. This isolates collection provides an overview of the distribution patterns of cosmopolitan marine culturable heterotrophic bacteria.

microbiology↗