Thiomicrorhabdus species, belonging to the family Piscirickettsiaceae in the phylum Pseudomonadotav are usually detected in various sulfur-rich marine environments. However, only a few bacteria of Thiomicrorhabdus have been isolated, and their ecological roles and environmental adaptations still require further understanding. Here, we report a novel strain, XGS-01^T, isolated from a coastal sediment, which belongs to genus Thiomicrorhabdus and is most closely related to Thiomicrorhabdus hydrogeniphila MAS2^T, with a sequence similarity of 97.8%. Phenotypic characterization showed that XGS-01^T is a mesophilic, sulfur-oxidizing, obligate chemolithoautotrophy, with carbon dioxide as its sole carbon source and oxygen as its sole electron acceptor. During thiosulfate oxidation, strain XGS-01^T can produce extracellular sulfur of elemental α-S₈, as confirmed via scanning electron microscopy and Raman spectromicroscopy. Polyphasic taxonomy results indicate that strain XGS-01^T represents a novel species of the genus Thiomicrorhabdus, named Thiomicrorhabdus lithotrophica sp. nov. Genomic analysis confirmed that XGS-01^T performed thiosulfate oxidation through a sox multienzyme complex, and harbored fcc and sqr genes for sulfide oxidation. Comparative genomics analysis among five available genomes from Thiomicrorhabdus species revealed that carbon fixation via the oxidation of reduced-sulfur compounds coupled with oxygen reduction is conserved metabolic pathways among members of genus Thiomicrorhabdus.

Two novel marine hydrogen- and sulfur-oxidizing bacteria, designated HSL1-7^T and HSL3-1^T, were isolated from mangrove sediments from Fujian Province, China. Strain HSL1-7^T exhibited Gram-negative, rod-shaped to slightly curved morphology with polar flagellum-driven motility, whereas strain HSL3-1^T was Gram-negative, rod-shaped and non-motile. Strain HSL1-7^T and HSL3-1^T were obligate chemolithoautotrophs, capable of using molecular hydrogen and thiosulfate as an energy source, and molecular oxygen and elemental sulfur as the electron acceptors for growth. Cellular fatty acid profiles revealed similar predominant components (C_16:1ω7c, C_16:0, C_18:1ω7c, and C_14:0) in both strains. Strains HSL1-7^T and HSL3-1^T were strongly diazotrophic, as demonstrated by ¹⁵N₂ fixation when a fixed nitrogen source was absent from the growth medium. The DNA G+C contents of strains HSL1-7^T and HSL3-1^T were determined to be 36.1% and 57.3%, respectively. Based on the 16S rRNA gene sequences, strains HSL1-7^T and HSL3-1^T exhibited the highest sequence similarities with Sulfurimonas marina B2^T (98.5% and 94.45%, respectively). Notably, the 16S rRNA gene sequence similarity between strains HSL1-7^T and HSL3-1^T was 93.19%, indicating that they represent distinct species within the genus Sulfurimonas. Comparative genomic analyses revealed the presence of diverse metabolic profiles in strains HSL1-7^T and HSL3-1^T, including carbon fixation, hydrogen oxidation, sulfur oxidation, and nitrogen fixation. The combined phenotypic, chemotaxonomic, and phylogenetic evidence, including average nucleotide identity and in silico DNA-DNA hybridization values, shows that strains HSL1-7^T and HSL3-1^T represent two novel species of the genus Sulfurimonas for which the names Sulfurimonas microaerophilic sp. nov. and Sulfurimonas diazotrophicus sp. nov. are proposed, with the type strains HSL1-7^T (=MCCC 1A18899^T = KCTC 25640^T) and HSL3-1^T (=MCCC 1A18844^T), respectively.

Pyrene is a pollutant in the environment and affects the health of living organisms. It is important to understand microbial-mediated pyrene resistance and the related molecular mechanisms due to its toxicity and biodegradability. Due to the unclear response mechanisms of bacteria to PAHs, this study detected the transcriptional changes in Escherichia coli under different pyrene concentrations using transcriptome sequencing technology. Global transcriptome analysis showed that the number of differentially expressed genes (DEGs) in multiple metabolic pathways increased with increasing concentrations of pyrene. In addition, the effects and toxicity of pyrene on Escherichia coli mainly included the up-regulation and inhibition of genes related to carbohydrate metabolism, membrane transport, sulfate reduction, various oxidoreductases, and multidrug efflux pumps. Moreover, we also constructed an association network between significantly differentially expressed sRNAs and key genes and determined the regulatory relationship and key genes of Escherichia coli under pyrene stress. Our study utilized pyrene as an exogenous stress substance to investigate the possible pathways of the bacterial stress response. In addition, this study provides a reference for other related research and serves as a foundation for future research.

Persistently high levels of abiotic stress define extreme environments. Even for adapted extremophiles, we argue this stress remains a continuous physiological challenge, necessitating energetically costly homeostasis. Crucially, this persistent pressure drives a self-reinforcing feedback loop across biological scales: it accelerates genomic evolution and concurrently reshapes ecological network architecture. Genomic innovations provide new traits for network reconfiguration, while the restructured network acts as a selective filter guiding subsequent evolution. This loop underpins extreme ecosystem resilience—the capacity for stress-induced adaptive restructuring. We synthesize mechanisms of this stress-adaptation interplay, propose testable hypotheses and outline experimental evolution approaches to validate this predictive framework for microbial responses to global change.

Hopanoids are a series of important lipid biomarkers in the bacterial cellular membranes that are found ubiquitously in different spatial and temporal environments. Squalene-hopane cyclase, a key and prerequisite molecular component of the hopanoid biosynthesis pathway, is encoded by the sqhC gene. To investigate the composition, niche, and distribution of microbial sqhC-containing communities, we analyzed hopanoid producer data and environmental parameters across different ecosystems on the basis of sequencing reads of peat samples from increasing gradient depths across peatland profile C in the Dajiuhu Peatland, as well as data collected from available published papers. The results indicated that the acidic Dajiuhu Peatland harbored mainly Acidobacteria (59.16%) among its sqhC-containing groups. The main composition of hopanoid producers in the peatland was different from that in other ecosystems, with Alphaproteobacteria found in soil (37.78%), cave (48.21%), hypersaline lagoon (34.04%), and marine (32.59%) ecosystems; Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria found in reef (100%), acid mine drainage (55.00%), and estuary, mangrove, and harbor (39.66%) ecosystems; and an unknown cluster found in freshwater (29.43%) and hot spring (89.58%) ecosystems. Compared with other phyla or sub-phyla, Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the most widespread, occurring in eight ecosystems. Peatland was significantly separated from the other nine ecosystem modules in the occurrence network, and the marine ecosystem had the greatest impact on the eco-network of sqhC microbes. An RDA indicated that pH, DO, salinity, and TOC had significant impacts on sqhC-containing microbial communities across the different ecosystems. Our results will be helpful to understanding the diversity, composition, and distribution of the sqhC community and its response to multiple environmental factors across different ecosystems.