Promotion and mechanisms of Bdellovibrio sp. Y38 on membrane fouling alleviation in membrane bioreactor

Exploiting predatory bacteria as biocontrol agents across ecosystems

Predatory bacteria have been increasingly known for their ubiquity in environments and great functional potentials in controlling unwanted microorganisms. Fundamental understanding of the predation mechanisms, population dynamics, and interaction patterns underlying bacterial predation is required for wise exploitation of predatory bacteria for enhancing ecoenvironmental, animal, and human health. Here, we review the recent achievements on applying predatory bacteria in different systems as biocontrol agents and living antibiotics as well as new findings in their phylogenetic diversity and predation mechanisms. We finally propose critical issues that deserve priority research and highlight the necessity to combine classic culture-based and advanced culture-independent approaches to push research frontiers of bacterial predation across ecosystems for promising biocontrol and therapy strategies towards a sustainable ecoenvironment and health.

Bioaugmentation with an aerobic denitrifying bacterium with quorum quenching activity for improved nitrogen removal and reduced membrane fouling in anoxic/oxic membrane bioreactor

In this study, an aerobic denitrifying bacterium with quorum quenching activity, Acinetobacter sp. WZL728, was inoculated into the anoxic/oxic membrane bioreactor (A/O-MBR) to study its effects on A/O-MBR performance. The pollutant removal and membrane fouling between A/O-MBR with WZL728 (EMBR) and A/O-MBR without WZL728 (CMBR) were compared. WZL728 increased the total nitrogen removal efficiency from 75.05% in CMBR to 91.03% in EMBR and extended the filtration cycle from 5.44 days in CMBR to 9.57 days in EMBR, which indicated that WZL728 improved the pollutant removal performance and mitigated membrane fouling of A/O-MBR. The concentration of N-acyl-homoserine lactones in the biocake of EMBR (EMBRB) was 11.23% of that in the biocake of CMBR (CMBRB). The content of extracellular polymeric substances (EPS) in EMBRB was 69.00% of that in CMBRB. The abundance of bacteria associated with EPS secretion (Alpthaproteobacteria) decreased and the abundance of bacteria associated with EPS degradation (Clostridia) increased in EMBRB. Valine, alanine and uridine diphosphate-N-acetylgalactosamine associated with protein and polysaccharide synthesis were significantly lower in EMBRB than those in CMBRB, which revealed the reason for the decrease of protein and polysaccharide content of EPS within EMBRB. This study provides useful information for improving A/O-MBR performance by probiotics.