Effect of dissolved organic matter on bacterial regrowth and response after ultraviolet disinfection.

The effect of dissolved organic matter (DOM) on bacterial regrowth in water after disinfection using ultraviolet (UV) light emitting diodes (UVLEDs) is still unclear. Herein, the regrowth and responses of Vibrio parahaemolyticus and Bacillus cereus were investigated after being exposed to UVLEDs at combined wavelengths (265 and 280 nm) in a phosphate-buffered saline consisting of Suwannee River natural organic matter (SRNOM) and Suwannee River fulvic acid (SRFA). Low-molecular-weight (MW) organic compounds, which may form into intermediary photoproducts, and indicate bacterial repair metabolism, were characterized through non-target screening using orbitrap mass spectrometry. This study demonstrates the ability of the UVLEDs-inactivated cells to regrow. After UV exposure, a considerable upregulation of RecA was observed in two strains. With increasing the incubation time, the expression levels of RecA in V. parahaemolyticus increased, which may be attributed to the dark repair mechanism. Coexisting anionic DOM affects both the disinfection and bacterial regrowth processes. The time required for bacterial regrowth after UV exposure reflects the time needed for the individual cells to reactivate, and it differs in the presence or absence of DOM. In the presence of DOM, the cells were less damaged and required less time to grow. The UVLEDs exposure results in the occurrence of low-MW organic compounds, including carnitine or acryl-carnitine with N-acetylmuramic acid, which are associated with bacterial repair metabolism. Overall, the results of this study expand the understanding of the effects of water matrices on bacterial health risks. This can aid in the development of more effective strategies for water disinfection.

Distinct spatiotemporal succession of bacterial generalists and specialists in the lacustrine plastisphere.

The assembly processes of generalists and specialists and their driving mechanisms during spatiotemporal succession is a central issue in microbial ecology but a poorly researched subject in the plastisphere. We investigated the composition variation, spatiotemporal succession, and assembly processes of bacterial generalists and specialists in the plastisphere, including non-biodegradable (NBMPs) and biodegradable microplastics (BMPs). Although the composition of generalists and specialists on NBMPs differed from that of BMPs, colonization time mainly mediated the composition variation. The relative abundance of generalists and the relative contribution of species replacement were initially increased and then decreased with colonization time, while the specialists initially decreased and then increased. Besides, the richness differences also affected the composition variation of generalists and specialists in the plastisphere, and the generalists were more susceptible to richness differences than corresponding specialists. Furthermore, the assembly of generalists in the plastisphere was dominated by deterministic processes, while stochastic processes dominated the assembly of specialists. The network stability test showed that the community stability of generalists on NBMPs and BMPs was lower than corresponding specialists. Our results suggested that different ecological assembly processes shaped the spatiotemporal succession of bacterial generalists and specialists in the plastisphere, but were less influenced by polymer types.

Occurrence and risk assessment of microplastics in the Lhasa River-a remote plateau river on the Qinghai-Tibet Plateau, China.

Microplastics (MPs) are ubiquitous in the aquatic environment and have received widespread attention worldwide as emerging pollutants. Urbanization and anthropogenic activities are the main sources of MPs in rivers; however, the MPs in plateau rivers with less human activities are not well understood. In this study, the pollution of MPs in the surface water and shore sediment of the Lhasa River from the Qinghai-Tibet Plateau was investigated, and a risk assessment was conducted. The abundance of MPs in the surface water and shore sediment of Lhasa River were 0.63 n/L and 0.37 n/g, respectively. MPs in surface water were mainly dominated by films (43.23%) and fibers (31.12%) in shape, transparent (54.25%) in color, and 0-0.5 mm (75.83%) in size, while MPs in the shore sediment were mainly fibers (43.69%) and fragments (36.53%), transparent (71.91%), and 0-0.5 mm (60.18%). PP and PE were the predominant polymer types, accounting for 44.55% and 30.79% respectively in the surface water and 32.51% and 36.01% respectively in the shore sediment. More notably, the polymer pollution index (H) of MPs in the Lhasa River was at hazard level III due to the high risk caused by PVC, but the pollution load index (PLI) was low at hazard level I. This study reveals that the remote river in the Qinghai-Tibet Plateau are polluted by MPs, and their potential risks to the vulnerable ecosystem deserve attention.

Antibiotic resistant bacteria and genes in shrimp aquaculture water: Identification and removal by ferrate(VI).

Enclosed shrimp culturing ponds are breeding environments for the spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the aquatic environment. This paper surveyed the presence of antibiotics, ARB, and ARGs in aquaculture waters and demonstrated their removal by ferrate (Fe(VI), FeO42-). Tetracyclines were the most prevalent antibiotics, followed by quinolones and ß-lactam. The bacterial resistance rates to three antibiotics were ordered as follows: amoxicillin (AMX) > oxytetracycline (OTC) > enrofloxacin (ENR). Proteobacteria, Verrucomicrobia, and Bacteroidetes were the predominant phyla, while sul1 and sul2 were the predominant ARGs. sul2 was positively correlated with Proteobacteria. Water quality parameters significantly influenced the dissemination of tetracycline resistance genes in aquacultures due to high organic waste accumulation. The removal efficiency of antibiotics by Fe(VI) depended on the structural moieties of antibiotics, with phenol-containing antibiotics more thoroughly oxidized (i.e., OTC) than amine-containing (ENR and AMX) antibiotics. Greater removal of antibiotics in aquaculture waters suggested that the constituents of farming water enhances the efficacy of antibiotics removal by Fe(VI). An acidic pH environment enhanced Fe(VI) inactivation of ARB over the circumneutral pH. The presented results are intended to improve aquaculture managing practices to minimize the antibiotic proliferation in aquaculture waters and the environment.

Large-scale pattern of resistance genes and bacterial community in the tap water along the middle and low reaches of the Yangtze River.

Antibiotic and metal resistance genes (ARGs and MRGs) in tap water are of great public health concern. However, very fewer studies focused on the relationship between resistance genes and opportunistic pathogens in tap water. In this study, the diversity and abundance of resistance genes and bacterial community from tap water at a large-scale along the middle and lower reaches of the Yangtze River were investigated. The total relative abundances of ARGs and MRGs were 2.95 × 10-3-1.22 × 10-1 and 1.93 × 10-3-1.20 × 10-1 copies/16S rRNA, respectively. The blaTEM and merP detected were major ARG and MRG subtypes, respectively. Mobile genetic elements (Intl1 and tnpA) showed significant correlations with the abundance of ARGs. Heavy metals also played a vital role in the co-selection of ARGs. Surprisingly, there were still eight opportunistic pathogens in tap water, among which Escherichia coli, Helicobacter pylori, Mycoplasma pneumoniae, and Porphyromonas gingivalis were the potential host of ARGs and MRGs. Escherichia coli had the highest abundance, while Bacillus anthracis had the highest detected frequency (100%), a widespread opportunistic pathogen in tap water.

Biotransformation of struvite by Aspergillus niger: phosphate release and magnesium biomineralization as glushinskite.

Struvite (magnesium ammonium phosphate-MgNH4 PO4 ·6H2 O), which can extensively crystallize in wastewater treatments, is a potential source of N and P as fertilizer, as well as a means of P conservation. However, little is known of microbial interactions with struvite which would result in element release. In this work, the geoactive fungus Aspergillus niger was investigated for struvite transformation on solid and in liquid media. Aspergillus niger was capable of solubilizing natural (fragments and powder) and synthetic struvite when incorporated into solid medium, with accompanying acidification of the media, and extensive precipitation of magnesium oxalate dihydrate (glushinskite, Mg(C2 O4 ).2H2 O) occurring under growing colonies. In liquid media, A. niger was able to solubilize natural and synthetic struvite releasing mobile phosphate (PO4 3- ) and magnesium (Mg2+ ), the latter reacting with excreted oxalate resulting in precipitation of magnesium oxalate dihydrate which also accumulated within the mycelial pellets. Struvite was also found to influence the morphology of A. niger mycelial pellets. These findings contribute further understanding of struvite solubilization, element release and secondary oxalate formation, relevant to the biogeochemical cycling of phosphate minerals, and further directions utilizing these mechanisms in environmental biotechnologies such as element biorecovery and biofertilizer applications.

Bisphenol A removal from a plastic industry wastewater by Dracaena sanderiana endophytic bacteria and Bacillus cereus NI.

Understanding the significance of plant-endophytic bacteria for bisphenol A (BPA) removal is of importance for any application of organic pollutant phytoremediation. In this research, Dracaena sanderiana with endophytic Pantoea dispersa showed higher BPA removal than uninoculated plants at 89.54 ± 0.88% and 79.08 ± 1.20%, respectively. Quantitative Real-Time PCR (qPCR) showed that P. dispersa increased from 3.93 × 107 to 8.80 × 107 16S rRNA gene copy number in root tissues from day 0 to day 5 which indicated that it could assist the plant in removing BPA during the treatment period. pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), conductivity, and salinity were reduced after 5 days of the experimental period. Particularly, BOD significantly decreased due to activities of the plants and microorganisms. Furthermore, an indigenous bacterial strain, Bacillus cereus NI, from the wastewater could remove BPA in high TDS and alkalinity condition of the wastewater. This work suggests that D. sanderiana plants could be used as a tertiary process in a wastewater treatment system and should be combined with its endophytic bacteria. In addition, B. cereus NI could also be applied for BPA removal from wastewaters with high TDS and salinity.