Draft genome sequence of Shimia marina CECT 7688T

Toxic effects of cadmium and lead exposure on intestinal histology, oxidative stress response, and microbial community of Pacific white shrimp Litopenaeus vannamei

Cadmium (Cd) and lead (Pb) are two hazardous pollutants that threaten shrimp farming. The intestine is an important organ for digestion and immunity. We separately exposed Pacific white shrimp Litopenaeus vannamei to 500 μg/L Cd or 500 μg/L Pb seawater for 7 days, and 45 shrimp from each group were used to evaluate the changes of intestinal histopathological, oxidative stress, and microbiota composition. After Cd and Pb exposure, shrimp intestine appeared significant mucosal damage and oxidative stress, and the microbiota variation were induced. Specifically, the abundance of the phyla Bacteroidetes and Actinobacteria were induced, that of Proteobacteria and Firmicutes were deduced. The abundances of putative beneficial bacteria (Lactobacillus, Weissella, Demequina, Formosa and Ruegeria) and potentially pathogenic bacteria (Vibrio and Photobacterium) were fluctuated. Furthermore, the nutrient metabolic function of intestinal microbes was significantly altered. We concluded that Cd and Pb exposure had negative effects on the intestinal health of shrimp.

Marine bacterial community analysis on 316L stainless steel coupons by Illumina MiSeq sequencing

In order to evaluate the corrosive action of microorganisms on 316L metal exposed directly to a marine environment, a system was designed to immerse coupons in seawater. After periods of 30, 60 and 90 days, the coupons were recovered, the corrosion rates evaluated and the biofilm samples on their surface were analyzed by 16S rRNA gene sequencing. The results of the corrosion rate showed an acceleration over the entire experimental period. Alpha diversity measurements showed higher rates after 60 days of the experiment, while abundance measurements showed higher rates after 90 days of exposure to the marine environment. The beta-diversity results showed a clear separation between the three conditions and proximity in the indices between replicates of the same experimental condition. The results of 16S rRNA gene sequencing showed that after 30 days of exposure to seawater, there was massive representativeness of the pioneer bacteria, Gamma and Alphaproteobacteria, with emphasis on the genera Alcanivorax, Oceanospirillum and Shewanella. At the 60-day analysis, the Gammaproteobacteria class remained dominant, followed by Alphaproteobacteria and Flavobacteria, and the main representatives were Flexibacter and Pseudoalteromonas. In the last analysis, after 90 days, a change in the described bacterial community profile was observed. The Gammaproteobacteria class was still the largest in diversity and OTUs. The most predominant genera in number of OTUs were Alteromonas, Bacteriovorax and, Nautella. Our results describe a change in the microbial community over coupons directly exposed to the marine environment, suggesting a redirection to the formation of a mature biofilm. The conditions created by the biofilm structure suggest said condition favor biocorrosion on the analyzed coupons.

Comparative Genomics of Thalassobius Including the Description of Thalassobius activus sp. nov., and Thalassobius autumnalis sp. nov

A taxogenomic study was conducted to describe two new Thalassobius species and to analyze the internal consistency of the genus Thalassobius along with Shimia and Thalassococcus. Strains CECT 5113^T, CECT 5114, CECT 5118^T, and CECT 5120 were isolated from coastal Mediterranean seawater, Spain. Cells were Gram-negative, non- motile coccobacilli, aerobic chemoorganotrophs, with an optimum temperature of 26°C and salinity of 3.5-5%. Major cellular fatty acids of strains CECT 5113^T and CECT 5114 were C_{18 : 1} ω7c/ω6c and C_{10 : 0} 3OH, G+C content was 54.4-54.5 mol% and were able to utilize propionate, L-threonine, L- arginine, and L-aspartate as carbon sources. They exhibited 98.3% 16S rRNA gene sequence similarity, 75.0-75.1 ANIb and 19.5-20.9 digital DDH to type strain of their closest species, Thalassobius maritimus. Based on these data, strains CECT 5113^T and CECT 5114 are recognized as a new species, for which the name Thalassobius activus is proposed, with strain CECT 5113^T (=LMG 29900^T) as type strain. Strains CECT 5118^T and CECT 5120 were found to constitute another new species, with major cellular fatty acids C_{18 : 1} ω7c/ω6c and C_{18 : 1} ω7c 11-methyl and a G+C content of 59.8 mol%; they were not able to utilize propionate, L-threonine, L- arginine or L-aspartate. Their closest species was Thalassobius mediterraneus, with values of 99.6% 16S rRNA gene sequence similarity, 79.1% ANIb and 23.2% digital DDH compared to the type strain, CECT 5383^T. The name Thalassobius autumnalis is proposed for this second new species, with strain CECT 5118^T (=LMG 29904^T) as type strain. To better determine the phylogenetic relationship of the two new species, we submitted 12 genomes representing species of Thalassobius, Shimia, and Thalassoccocus, to a phylogenomic analysis based on 54 single protein-encoding genes (BCG54). The resulting phylogenomic tree did not agree with the current genera classification, as Thalassobius was divided in three clades, Thalassobius sensu stricto (T. mediterraneus, T. autumnalis sp. nov., and T. gelatinovorus), Thalassobius aestuarii plus the three Shimia spp (S. marina, S. haliotis, and Shimia sp. SK013) and finally, Thalasobius maritimus plus T. activus sp. nov. Thalassococcus halodurans remained apart from the two genera. Phenotypic inferences from explored genomes are presented.