Intact aquifer sediments were collected to obtain As-resistant bacteria from the Hetao basin. Two strains of aerobic As-resistant bacteria (Pseudomonas sp. M17-1 and Bacillus sp. M17-15) were isolated from the aquifer sediments. Those strains exhibited high resistances to both As(III) and As(V). Results showed that both strains had arr and ars genes, and led to reduction of dissolved As(V), goethite-adsorbed As(V), scorodite As(V) and sediment As(V), in the presence of organic carbon as the carbon source. After reduction of solid As(V), As release was observed from the solids to solutions. Strain M17-15 had a higher ability than strain M17-1 in reducing As(V) and promoting the release of As. These results suggested that the strains would mediate As(V) reduction to As(III), and thereafter release As(III), due to the higher mobility of As(III) in most aquifer systems. The processes would play an important role in genesis of high As groundwater.

The impact of siderophore produced by arsenic-resistant bacterium Pseudomonas PG12 on FeAsO4 dissolution and plant growth were examined. Arsenic-hyperaccumulator Pteris vittata was grown for 7 d in 0.2-strength Fe-free Hoagland solution containing FeAsO4 mineral and PG12-siderophore or fungal-siderophore desferrioxamine B (DFOB). Standard siderophore assays indicated that PG12-siderophore was catecholate-type. PG12-siderophore was more effective in promoting FeAsO4 dissolution, and Fe and As plant uptake than DFOB. Media soluble Fe and As in PG12 treatment were 34.6 and 3.07 μM, 1.6- and 1.4-fold of that in DFOB. Plant Fe content increased from 2.93 to 6.24 g kg−1 in the roots and As content increased from 14.3 to 78.5 mg kg−1 in the fronds. Besides, P. vittata in PG12 treatment showed 2.6-times greater biomass than DFOB. While P. vittata fronds in PG12 treatment were dominated by AsIII, those in DFOB treatment were dominated by AsV (61–77%). This study showed that siderophore-producing arsenic-resistant rhizobacteria may have potential in enhancing phytoremediation of arsenic-contaminated soils.

The main aim of the study was to evaluate the role of scallop hatcheries as source of the floR and cmlA genes. A number of 133 and 121 florfenicol-resistant strains were isolated from scallop larval cultures prior to their transfer to seawater and from effluent samples from 2 commercial hatcheries and identified by 16S rRNA gene sequence analysis, observing a predominance of the Pseudomonas, Pseudoalteromonas and Halomonas genera and exhibiting an important incidence of co-resistance to streptomycin, oxytetracycline and co-trimoxazole. A high percentage of strains from both hatcheries carried the floR gene (68.4% and 89.3% of strains), whereas a lower carriage of the cmlA gene was detected (27.1% and 54.5% of strains). The high prevalence of floR-carrying bacteria in reared scallop larvae and hatchery effluents contributes to enrich the marine resistome in marine environments, prompting the need of a continuous surveillance of these genes in the mariculture environments.

In order to examine the influence of discharge from different rivers from peninsular India and urban sewage on intensity and dissemination of heterotrophic, indicator and pathogenic bacteria, a study was carried out during peak discharge period along coastal Bay of Bengal. The coastal Bay received freshwater inputs from the river Ganges while Godavari and Krishna contributed to the south. Contrasting difference in salinity, temperature, nutrients and organic matter was observed between north and south east coast of India. The highest heterotrophic, indicator and pathogenic bacterial abundance was observed in the central coastal Bay that received urban sewage from the major city. Intensity and dissemination of heterotrophic, indicator and pathogenic bacteria displayed linear relation with magnitude of discharge. The coliform load was observed up to 100km from the coast suggesting that marine waters were polluted during the monsoon season and its impact on the ecosystem needs further studies.

Using enrichment culture technique, three isolates marked as ODB-1, ODB-2 and ODB-3, were selected from oil contaminated seawater. 16S rDNA gene sequencing indicated that ODB-1 affiliated with Pseudomonas sp. while ODB-2 and ODB-3 affiliated with Brevundimonas sp. Subsequently, the bacterial cells were immobilized on the surface of expanded graphite (EG), expanded perlite (EP) and bamboo charcoal (BC). Among the three isolates, ODB-1 showed a strong binding to the bio-carriers through extracellular polysaccharides, while ODB-2 and ODB-3 made the adhesion to bio-carrier through direct physical adsorption. The immobilized bacteria exhibited good salinity tolerance compared with the planktonic bacteria. Their total diesel oil removal rates were more than 85% after 6 days’ incubation. Adsorption–biodegradation process played an important role in the oil-pollution remediation. EG-bacteria system was treated as a promising remediation method, which achieved nearly 100% removal of diesel oil. Thereinto, over 83% removal of diesel oil owed to biodegradation.

Rhamnolipid is a biosurfactant produced by several Pseudomonas species, and can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid is believed to have minimal adverse impact on the soil and groundwater after usage. Applications of rhamnolipid to improve irrigation in agricultural soils thus have obvious advantages over other chemical wetting agents, especially under drought conditions. Due to global warming, soil amendment with biochar has been commonly practiced in agricultural soils to increase the soil water-holding capacity. As such, rhamnolipid transport in biochar-amended agricultural soils needs to be characterized. In this research, we found that rhamnolipid transport in biochar-amended agricultural soils was hindered by retardation (equilibrium adsorption) and deposition (kinetic adsorption), which was well represented by the advection-dispersion equation based on a local equilibrium assumption. A linear equilibrium adsorption was assumed in the advection-dispersion equation simulation, which was proved to be acceptable by studying the breakthrough curves. Both rhamnolipid equilibrium adsorption and kinetic adsorption increased with the increase of the biochar content in the agricultural soil.

Hundreds of millions of people are at risk from drinking arsenic (As)-contaminated groundwater in the world, making As removal from aquatic systems of utmost importance. However, characteristics of As removal by bacteria-induced ferrihydrite and coupled with redox processes are still not clear. Two-line ferrihydrite was formed in the presence of aerobic Fe(II)-oxidizing bacterium, Pseudomonas sp. strain GE-1. Arsenic co-precipitation with and adsorption onto ferrihydrite induced by Pseudomonas sp. strain GE-1 and redox processes of As were investigated. Results demonstrated that co-precipitation performed better in As(V) removal than As(III) removal, while adsorption showed higher capacity for As(III) removal. X-ray absorption near-edge spectroscopy (XANES) indicated that As(III) oxidation occurred in solid phases during co-precipitation and adsorption. Detection of As species in solution showed that As(V) was reduced to As(III) during co-precipitation, although no As(V) reduction occurred during adsorption. Arsenic immobilization by Pseudomonas sp. strain GE-1-induced ferrihydrite in the presence of the strains may be applied as an alternative remediation strategy.

An erythromycin-degrading bacterium was isolated from the activated sludge of a sewage treatment plant (STP). Based on the morphological and physiological characteristics, the isolated strain was identified and named as Pseudomonas sp. ERY-E. In an inorganic salt medium inoculated at 1 % (v/v) of ERY-E strain containing 50 mg/L of erythromycin (ERY), the removal efficiency of ERY as high as 83.7 % was obtained under the optimum conditions with temperature of 30 °C, pH of 7.0, and 10 mg/L of yeast as the external carbon source. Subsequently, the ERY-E strain was used for bioaugmenting a biological aerated filter (BAF) to treat surface water containing low-concentration ERY. The influence of hydraulic retention time (HRT) and air-liquid ratio (A/L) on the performance of BAF was investigated. The average removal efficiencies of ERY and permanganate index (CODMₙ) were about 60.6 and 26.1 % in bioaugmented system (BAF₂) and 26.9 and 26.0 % in unbioaugmented system (BAF₁), respectively, under the optimum conditions with HRT of 4.0 h and A/L of 4:1 at steady state. Due to the stable removal of CODMₙ in BAF₂ as compared with BAF₁, it can be concluded that the introduction of ERY-E strain could collaborate with the indigenous microorganisms to attain a better ERY removal efficiency. As a result, the bioaugmented BAF method can be considered as an alternative technology for the treatment of surface water containing low-concentration emerging pollutants.

The aim of this study was to evaluate the efficiency of a passive point-of-use treatment system, namely, a polyvinyl (alcohol) (PVA) nanofiber membrane/activated carbon column, for the treatment of harvested rainwater. The efficiency of SMI-Q10 [quaternized poly (styrene-co-maleimide)] nanofiber membrane disks placed in a filtration assembly for the treatment of surface water (Plankenburg River, Western Cape, South Africa) and harvested rainwater was also assessed. Two rainwater harvesting tanks were installed at the Welgevallen Experimental farm, Stellenbosch, South Africa, with the filtration system intermittently attached to the tanks for collection of rainwater samples throughout the study period. Parameters used to monitor the filtration systems included heterotrophic bacteria, Escherichia coli, and total coliform enumeration and the presence/absence of adenovirus. When compared to drinking water guidelines, the results indicated that 3 L of potable water could be produced by the synthesized PVA nanofiber membrane/activated carbon column. However, PCR assays indicated that adenovirus and numerous bacteria such as Klebsiella spp., Legionella spp., Pseudomonas spp., and Yersinia spp. were not effectively removed by the filtration system utilized. Additionally, the SMI-Q10 nanofiber membrane disks did not remove viruses from the river or tank water samples as bovine adenovirus 3 strain, simian adenovirus, and human adenovirus A strain were detected in all water samples analyzed. Thus, while the microfiltration system was efficient in reducing the level of indicator organisms to within drinking water standards, further optimization of the electrospun filtration membranes is required as molecular analysis revealed that numerous opportunistic bacterial pathogens and viruses persisted after filtration.

Bioaccumulation of Cd²⁺in soil bacteria might represent an important route of metal transfer to associated mycorrhizal fungi and plants and may have potential as a tool to accelerate Cd²⁺extraction in the bioremediation of contaminated soils. The present study examined the bioaccumulation of Cd²⁺in 15 bacterial strains representing three phyla (Firmicutes, Proteobacteria, and Bacteroidetes) that were isolated from the rhizosphere, ectomycorrhizae, and fruitbody of ectomycorrhizal fungi. The strains Pseudomonas sp. IV-111-14, Variovorax sp. ML3-12, and Luteibacter sp. II-116-7 displayed the highest biomass productivity at the highest tested Cd²⁺concentration (2 mM). Microscopic analysis of the cellular Cd distribution revealed intracellular accumulation by strains Massilia sp. III–116-18, Pseudomonas sp. IV-111-14, and Bacillus sp. ML1-2. The quantities of Cd measured in the interior of the cells ranged from 0.87 to 1.31 weight % Cd. Strains originating from the rhizosphere exhibited higher Cd²⁺accumulation efficiencies than strains from ectomycorrhizal roots or fruitbodies. The high Cd tolerances of Pseudomonas sp. IV-111-16 and Bacillus sp. ML1-2 were attributed to the binding of Cd²⁺as cadmium phosphate. Furthermore, silicate binding of Cd²⁺by Bacillus sp. ML1-2 was observed. The tolerance of Massilia sp. III-116-18 to Cd stress was attributed to a simultaneous increase in K⁺uptake in the presence of Cd²⁺ions. We conclude that highly Cd-tolerant and Cd-accumulating bacterial strains from the genera Massilia sp., Pseudomonas sp., and Bacillus sp. might offer a suitable tool to improve the bioremediation efficiency of contaminated soils.