Objective To explore the diversity of culturable bacteria in the mudflat sediments of the Pearl River Estuary in Guangdong Province and to mine strain resources capable of degrading microplastics from these sediments.Methods Five media were used for microbial isolation, and phylogenetic analysis was performed by MEGA-X software. The polyethylene terephthalate (PET) medium was selected to screen PET microplastic-degrading strains, and then gene function annotation was performed.Results A total of 265 bacterial strains belonging to 71 genera, 32 families of 4 phyla were isolated, including 168 (63.40%) strains of Pseudomonadota, 38 (14.34%) strains of Actinomycetota, 31 (11.70%) strains of Bacillota, and 28 (10.56%) strains of Bacteroidota. Based on the homology of 16S ribosomal RNA (16S rRNA) gene sequences, it was hypothesized that 59 of these strains might be potential new species. From the isolated strains, one PET microplastic-degrading strain was screened.Conclusion This study successfully obtained unique microbial resources from the tidal flats of Xiangzhou District, Zhuhai City and one strain capable of degrading PET and using PET as the sole carbon source.

The karst seasonal rainforest of northern tropics in Guangxi is a unique forest ecosystem in China. However, the soil microbial diversity and its maintenance mechanism remain unclear.Objective This study explored the distribution characteristics and influencing factors of soil bacterial diversity in a karst seasonal rainforest of northern tropics, aiming to provide a reference for analyzing soil microbial diversity and its maintenance mechanisms in this region.Methods Soil samples were collected from a long-term dynamic monitoring plot in the karst rainforest of northern tropics (referred to as the Nonggang plot). The composition and distribution pattern of soil bacterial community were analyzed by 16S rRNA gene amplicon sequencing, and the potential influencing factors were identified by the correlation analysis.Results The soil in Nonggang plot harbored a total of 5 841 bacterial operational taxonomic units (OTUs), which were annotated to 1 501 species belonging to 677 genera, 373 families, 242 orders, 104 classes of 35 phyla. The dominant bacterial phyla were Proteobacteria, Actinobacteriota, and Acidobacteriota. The dominant bacterial phylum was Proteobacteria in both the depression and the slope habitats, and Actinobacteriota in the hilltop habitat. The number of total and specific bacterial OTUs displayed a pattern of depression>slope>hilltop habitats. The hilltop habitat association had the fewest total OTUs but the most specific OTUs. The soil bacterial alpha diversity indexes (Chao1, Sobs, Shannon, and Simpson) were not significantly different between the depression and slope habitats, while they were significantly lower in the hilltop habitat. Similarly, the hilltop habitat association had the lowest bacterial alpha diversity indexes than the other associations. The principal coordinate analysis (PCoA) of beta diversity showed differences in the bacterial communities among different habitats and associations. The linear discriminant analysis effect size (LEfSe) identified more differential groups in the depression and hilltop habitats than in the slope habitat. The Spearman correlation analysis, Mantel test and redundancy analysis (RDA) indicated that elevation was the primary factor influencing the distribution of soil bacteria in Nonggang plot, followed by soil organic carbon, available nitrogen, and available phosphorus. Tax4Fun predicted that there were significant differences in the function of soil bacterial communities among different habitats and associations, especially in the hilltop habitat.Conclusion This study revealed the community composition and diversity distribution pattern of soil bacteria in Nonggang plot and identified elevation as the primary factor affecting the distribution. These results contribute to the understanding of soil bacterial diversity and its maintaining mechanism in the karst seasonal rainforest of the northern tropics in Guangxi.

Objective To explore the diversity of halophilic bacteria in the magnesium sulfate-subtype Da Qaidam Salt Lake, compare the effects of different culture conditions on the diversity of halophilic bacteria, and screen the extracellular functional enzymes of halophilic bacteria.Methods Illumina MiSeq was used to analyze the diversity of bacteria in the Da Qaidam Salt Lake. Thirteen media, 2 salinities, 8 enrichment culture periods, and 6 dilution gradients were selected to isolate halophilic bacteria, and the taxonomic status of the strains was determined by 16S rRNA gene sequencing and BLAST sequence alignment. According to the sequencing results, 45 representative strains of different species belonging to 18 genera were selected and 7 media were used to screen the strains with activities of functional enzymes including protease, cellulase, amylase, and esterase.Results A total of 244 bacterial OTUs were obtained by culture-free high-throughput sequencing in the Da Qaidam Salt Lake. The strains with clear taxonomic status were annotated to 153 genera, 133 families, 92 orders, 53 classes of 19 phyla, with Pseudomonadota and Actinomycetota being the dominant phyla. A total of 593 strains of halophilic bacteria were isolated from the mixed water and mud samples of the Da Qaidam Salt Lake, belonging to 22 genera, 12 families, 8 orders, 5 classes of 4 phyla, of which 11 strains may belong to potential new species. Pseudomonadota and Bacillota were the dominant phyla, and Halomonas, Virgibacillus, and Bacillus were the dominant genera. The number of halophilic bacteria isolated under the culture with 10% NaCl was significantly higher than that with 18% NaCl, indicating that moderately halophilic bacteria were dominant among culturable halophilic bacteria. The media with better isolation performance were 2216E, 1/2 R2A, 1/10 2216E, and 1/10 TSA, all of which are oligotrophic media. The optimal enrichment culture periods ranged from 7 to 30 days. The undiluted samples obtained the best isolation results, followed by dilution gradients of 10^-1 and 10^-2. Among the 45 representative strains, 40.0%, 31.1%, 40.0%, and 82.22% of the strains had activities of protease, cellulase, amylase, and esterase, respectively.Conclusion Optimization of the isolation and culture conditions can significantly improve the diversity of halophilic bacteria that can be cultured in salt lakes. The high diversity and high halophilic enzyme activities of the culturable halophilic bacteria from the Da Qaidam Salt Lake provide a basis for further application of these halophilic bacteria.