Ancrocorticia populi gen. nov., sp. nov, isolated from the symptomatic bark of Populus × euramericana canker

Metagenomic and Culturomics Analysis of Microbial Communities within Surface Sediments and the Prevalence of Antibiotic Resistance Genes in a Pristine River: The Zaqu River in the Lancang River Source Region, China

Microbial communities inhabiting sedimentary environments in river source regions serve as pivotal indicators of pristine river ecosystems. While the correlation between antibiotic resistome and pathogenicity with core gut bacteria in humans is well established, there exists a significant knowledge gap concerning the interaction of antibiotic resistance genes (ARGs) and human pathogenic bacteria (HPB) with specific microbes in river source basins, often referred to as "terrestrial gut". Understanding the microbial composition, including bacteria and resident genetic elements such as ARGs, HPB, Mobile Genetic Elements (MGEs), and Virulence Factors (VFs), within natural habitats against the backdrop of global change, is imperative. To address this gap, an enrichment-based culturomics complementary along with metagenomics was conducted in this study to characterize the microbial biobank and provide preliminary ecological insights into profiling the dissemination of ARGs in the Lancang River Source Basin. Based on our findings, in the main stream of the Lancang River Source Basin, 674 strains of bacteria, comprising 540 strains under anaerobic conditions and 124 under aerobic conditions, were successfully isolated. Among these, 98 species were identified as known species, while 4 were potential novel species. Of these 98 species, 30 were HPB relevant to human health. Additionally, bacA and bacitracin emerged as the most abundant ARGs and antibiotics in this river, respectively. Furthermore, the risk assessment of ARGs predominantly indicated the lowest risk rank (Rank Ⅳ) in terms of endangering human health. In summary, enrichment-based culturomics proved effective in isolating rare and unknown bacteria, particularly under anaerobic conditions. The emergence of ARGs showed limited correlation with MGEs, indicating minimal threats to human health within the main stream of the Lancang River Source Basin.

Ancrocorticia populi gen. nov., sp. nov, isolated from the symptomatic bark of Populus × euramericana canker

A Gram-staining positive facultative anaerobic, non-motile strain, sk1b4^T , was isolated from canker of symptomatic bark tissue of a Populus × euramericana. 16S rRNA gene sequence analyses showed that strain sk1b4^T shared the highest similarity with Arcanobacterium phocisimile (94.1%). Within the phylogenetic tree, the novel isolate formed a distinct branch from Actinobaculum, Arcanobacterium, and Trueperella. The percentage of conserved proteins calculated from genomic sequence indicated a low level of relatedness between the novel strain and its phylogenetic neighbors. Growth of the novel strain occurred at temperatures between 10 and 41°C, and within a pH range of 6.0-9.0; optimal growth occurred at 30°C and at pH 6.0-9.0. Growth also occurred within a NaCl concentration of 1%-5% (w/v). The major fatty acids of the strain were C_14:0 , C_16:0 , and C_18:1 ω9c_, and major polar lipids were glycolipid, phosphatidylinositol mannoside, phospholipid, diphosphatidylglycerol, and phosphatidylglycerol. Respiratory quinone was absent. On the basis of phenotypic and genotypic characteristics, we propose that the novel isolate should be classified as a novel species in a new genus: Ancrocorticia populi gen. nov., sp. nov. The type strain is sk1b4^T (=CFCC 14564^T = KCTC 39919^T ).