Comparative genome analysis of the genus Hydrotalea and proposal of the novel species Hydrotalea lipotrueae sp. nov., isolated from a groundwater aquifer in the south of Mallorca Island, Spain

Undisclosed contribution of microbial assemblages selectively enriched by microplastics to the sulfur cycle in the large deep-water reservoir

The accumulation of microplastics in reservoirs due to river damming has drawn considerable attention due to their potential impacts on elemental biogeochemical cycling at the watershed scale. However, the effects of plastisphere communities on the sulfur cycle in the large deep-water reservoir remain poorly understood. Here, we collected microplastics and their surrounding environmental samples in the water and sediment ecosystems of Xiaowan Reservoir and found a significant spatiotemporal pattern of microplastics and sulfur distribution in this Reservoir. Based on the microbial analysis, plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) involved in the sulfur cycle were enriched in the plastisphere of water and sediment, respectively. Typical thiosulfate oxidizing bacteria Limnobacter acted as keystone species in the plastisphere microbial network. Sulfate, oxidation reduction potential and organic matter drove the variations of the plastisphere. Environmental filtration significantly affected the plastisphere communities, and the deterministic process dominated the community assembly. Furthermore, predicted functional profiles related to sulfur cycling, compound degradation and membrane transport were significantly enriched in the plastisphere. Overall, our results suggest microplastics as a new microbial niche exert different effects in water and sediment environments, and provide insights into the potential impacts of the plastisphere on the sulfur biogeochemical cycle in the reservoir ecosystem.

Metagenomics of two aquifers with thermal anomalies in Mallorca Island, and proposal of new uncultivated taxa named following the rules of SeqCode

Groundwater offers an intriguing blend of distinctive physical and chemical conditions, constituting a challenge for microbial life. In Mallorca, the largest island of Balearic archipelago, harbours a variety of thermal anomalies (i.e., geothermal manifestation where surface aquifers exhibiting temperatures exceeding the regional average). The metagenomes of two aquifers in the centre and southern of the island showed Pseudomonadota to be the most represented phylum when using extracted 16S rRNA gene sequences. However, the microbial structures within and between aquifers were remarkably diverse but similar in their metabolic profiles as revealed by the metagenome-assembled genomes (MAGs) pointing to a prevalence of aerobic chemolithoautotrophic and heterotrophic metabolisms, especially in the Llucmajor aquifer. Also, some evidences of anaerobic lifestyles were detected, which would indicate that these environments either could suffer episodes of oxygen depletion or the anaerobes had been transported from deeper waters. We believe that the local environmental factors (temperature, external inputs or chemistry) seem to be more relevant than the connection and, eventually, transport of microbial cells within the aquifer in determining the highly divergent structures. Notably, most of the reconstructed genomes belonged to undescribed bacterial lineages and from them two high-quality MAGs could be classified as novel taxa named following the rules of the Code for Nomenclature of Prokaryotes Described from Sequence Data (SeqCode). Accordingly, we propose the new species and genus Costitxia debesea gen. nov., sp. nov., affiliated with the novel family Costitxiaceae fam. nov., order Costitxiales ord. nov. and class Costitxiia class. nov.; and the new new species and genus Lloretia debesea gen. nov. sp. nov. affiliated with the novel family Lloretiaceae fam. nov.

Description and genomic characterization of Gallaecimonas kandeliae sp. nov., isolated from the sediments of mangrove plant Kandelia obovate

The genus Gallaecimonas, proposed by Rodríguez-Blanco et al. (Int J Syst Evol Microbiol 60:504-509, 2010), is mainly isolated from marine environments. So far, only three species have been identified and characterized in this genus. In this study, a new Gallaecimonas strain named Q10^T was isolated from the sediments of mangrove plant Kandelia obovate taken from Dapeng district, Shenzhen, China. Strain Q10^T was a Gram-stain-negative, non-motile, strictly aerobic, rod-shaped bacterium, and grew with 0-8.0% (w/v) NaCl, at 10-45 °C and at pH 5.5-8.5. Phylogenetic analysis indicated that strain Q10^T and the three Gallaecimonas species formed a clade in the tree, with 16S rRNA gene sequence similarities ranging from 96.0 to 97.0%. The major respiratory quinone is Q8. The polar lipids comprised aminolipid, aminophospholipid, diphosphatidylglycerol, glycolipid, phosphatidylethanolamine, phosphatidylglycerol, glycophospholipid and phospholipid. The predominant fatty acids are C_16:0, C_17:1ω8c, summed feature 3 (C_16:1ω7c/C_16:1ω6c), and iso-C_16:0. The complete genome of strain Q10^T is 3,836,841 bp with a G+C content of 62.6 mol%. The orthologous proteins analysis revealed 55 unique proteins in strain Q10^T related to important biological processes, especially three frataxins related to iron-sulfur cluster assembly, which may play a pivotal role in environmental adaptability of this species. Based on polyphasic taxonomic data, strain Q10^T is considered to represent a novel species within the genus Gallaecimonas, for which the name Gallaecimonas kandelia sp. nov. is proposed. The type strain is Q10^T (=KCTC 92860^T=MCCC 1K08421^T). These results contribute to a better understanding of general features and taxonomy of the genus Gallaecimonas.