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The accumulation of plastic waste in the environment has become a serious environmental problem worldwide. Biodegradable plastics, such as polyhydroxyalkanoate (PHA), could serve as green alternatives to petroleum-based plastics. In this study, a mixed microbial culture was enriched under feast/famine conditions using a sequencing batch reactor (SBR) with acetate as a carbon source. The enrichment could accumulate a maximum PHA concentration of 32.3% gPHA/g mixed liquor suspended solids (MLSS) in the 12th cycle of SBR operation. The microbial community in this sludge sample was analyzed using 16 S rRNA gene amplicon sequencing (MiSeq). The results showed the dominance of Proteobacteria, represented by Alphaproteobacteria (13.26% of total sequences), Betaproteobacteria (51.37% of total sequences), and Gammaproteobacteria (23.44% of total sequences). Thauera (Betaproteobacteria) had the highest relative abundance, accounting for 48.88% of the total sequences. PHA-accumulating microorganisms in the enrichment were detected using fluorescence in situ hybridization (FISH) and a fluorescent dye, Nile blue A. Alphaproteobacteria and Betaproteobacteria were capable of accumulating PHA, while no Gammaproteobacteria were detected. Thauera spp. from Betaproteobacteria constituted 80.3% of the total PHA accumulating cells. [ABSTRACT FROM AUTHOR]

The antibiotic tiamulin (TIA) is common and widely used medication for dysentery eradication in swine productions. Tiamulin persists in livestock manure, and its residues have been found in various environment. This work obtained four tiamulin-degrading enriched bacterial consortia from a covered anaerobic lagoon system and a stabilized pond system of swine farms. Tiamulin was efficiently removed by the enriched cultures at the concentrations between 2.5 and 200 mg/L, with a removal of 60.1–99.9% during 16 h and a degradation half-life of 4.5–15.7 h. The stabilized pond system cultured with taimulin solely could eliminate tiamulin at the highest rates. The logistic substrate degradation model fit most of the experimental data. Next-generation amplicon sequencing was conducted, and it was found that the bacterial community was significantly impacted by the inoculum source, nutrient addition, and high tiamulin concentrations. Principal coordinate analysis (PCoA) indicated the similarity of bacterial communities in the original enriched samples and the 2.5 mg/L tiamulin-removed cultures. The 200 mg/L consortia were rather different and became similar to the other 200 mg/L consortia from different sources and cultures without nutrient supplementation. Shannon and Simpson indices suggested a reduction in bacterial diversity at high concentrations. The microbes that had high growth in the most efficient enriched culture, or which were abundant in all samples, or which increased with higher tiamulin concentrations were likely to be the major tiamulin-degrading bacteria. This is the first report suggested the possible roles of Achromobacter, Delftia, Flavobacterium, Pseudomonas, and Stenotrophomonas in tiamulin degradation. [ABSTRACT FROM AUTHOR]

17α-Methyltestosterone (MT) is widely used synthetic androgenic steroid in the tilapia aquaculture industry for masculinization: a sex reversal process in which hormones are utilized to induce production of male fish. Although MT is beneficial for aquaculture, release of residual MT can cause adverse effects on wild organisms. The aims of this study were to identify MT-degrading bacteria and to characterize their degradation abilities under the conditions experienced in the environment. Nocardioides nitrophenolicus S303, Acinetobacter radioresistens B051, and Ochrobactrum haematophilum B052 were the most efficient MT-degrading bacterial strains, with the shortest degradation half-life of 10–70 h. The MT degradation by Acinetobacter and Ochrobactrum has not been reported before. After comparing their degradation rates and for reason of biosafety, N. nitrophenolicus S303 was selected for further study. Although this strain degraded MT and testosterones, it could not degrade estrogens (estrone, 17β-estradiol, nor 17α-ethinylestradiol). Glucose amendment did not affect the MT degradation rate. No metabolites with androgenic activity were observed after 264-h treatment with this strain under aerobic conditions. Methandrostenolone was found as the major intermediate during 39–90 h. This is the first report indicating the 1,2-dehydrogenase activity in steroid clevage in N. nitrophenolicus. Our study provides important information concerning the application of N. nitrophenolicus S303 to enhance MT degradation in the environment. [ABSTRACT FROM AUTHOR]