Genome-Centric Metatranscriptomic Characterization of a Humin-Facilitated Anaerobic Tetrabromobisphenol A-Dehalogenating Consortium.

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in electronics manufacturing, has caused global contamination due to improper e-waste disposal. Its persistence, bioaccumulation, and potential carcinogenicity drive studies of its transformation and underlying (a)biotic interactions. This study achieved an anaerobic enrichment culture capable of reductively dehalogenating TBBPA to the more bioavailable bisphenol A. 16S rRNA gene amplicon sequencing and quantitative PCR confirmed that successive dehalogenation of four bromide ions from TBBPA was coupled with the growth of both Dehalobacter sp. and Dehalococcoides sp. with growth yields of 5.0 ± 0.4 × 108 and 8.6 ± 4.6 × 108 cells per µmol Br- released (N = 3), respectively. TBBPA dehalogenation was facilitated by solid humin and reduced humin, which possessed the highest organic radical signal intensity and reducing groups -NH2, and maintained the highest dehalogenation rate and dehalogenator copies. Genome-centric metatranscriptomic analyses revealed upregulated putative TBBPA-dehalogenating rdhA (reductive dehalogenase) genes with humin amendment, cprA-like Dhb_rdhA1 gene in Dehalobacter species, and Dhc_rdhA1/Dhc_rdhA2 genes in Dehalococcoides species. The upregulated genes of lactate fermentation, de novo corrinoid biosynthesis, and extracellular electron transport in the humin amended treatment also stimulated TBBPA dehalogenation. This study provided a comprehensive understanding of humin-facilitated organohalide respiration.

Widespread but Poorly Understood Bacteria: Candidate Phyla Radiation.

Candidate Phyla Radiation (CPR) bacteria is a bacterial division composed mainly of candidate phyla bacteria with ultra-small cell sizes, streamlined genomes, and limited metabolic capacity, which are generally considered to survive in a parasitic or symbiotic manner. Despite their wide distribution and rich diversity, CPR bacteria have received little attention until recent years, and are therefore poorly understood. This review systematically summarizes the history of CPR research, the parasitic/symbiotic lifestyle, and the ecological distribution and unique metabolic features of CPR bacteria, hoping to provide guidance for future ecological and physiological research on CPR bacteria.