Cultivatable bacterial community at a fresh water nullah contaminated with household sewage and industrial waste is more diverse and populated compared to non-polluted water

The effect of environmental pollutants on living organisms can be assessed by studying the changes in the indigenous microbial community. Therefore, in the present study, cultivatable bacterial community in non-polluted as well as household sewage and industrially polluted water of Lai Nullah flowing through Islamabad-Rawalpindi, Pakistan was analysed. Bacterial community composition and population present in the polluted water was significantly different from the non-polluted water (P < 0.05). Non-polluted water had much fewer species and population of bacteria compared to polluted water. Sequence analysis of bacterial 16S rRNA gene revealed that Citrobacter freundii, Klebsiella pneumoniae, Escherichia coli, Lactobacillus plantarum, Geobacillus stearothermophilus, Enterococcus faecalis, Acinetobacter guillouiae, Ralstonia sp., Comamonas sp. and Stenotrophomonas maltophilia were specific to the polluted water. On the other hand, Aeromonas veronii, Exiguobacterium sp. and Lysinibacillus macroides were only found in the non-polluted water. Among measured physicochemical parameters, higher colony count in the polluted water was best correlated with higher biological oxygen demand, phosphate, sodium and chloride values (Spearman's rho = 0.85). Concentration of heavy metals such as cadmium, chromium, copper, nickel and lead were below 0.03μg/mL at all the study sites. During plate assay, bacterial strains found at polluted sites showed resistance to selected heavy metals with highest minimum inhibitory concentration for lead (8mM) followed by copper (5mM), nickel (3mM) and cadmium (1mM). All the bacterial isolates also showed various levels of resistance against antibiotics ampicillin, tetracycline, ciprofloxacin and vancomycin using broth microdilution method. Current research provides new insight into the effect of household sewage and industrially polluted water of Lai Nullah on the indigenous bacteria".

BIOAUGMENTATION OF ACRYLAMIDE-DEGRADING BACTERIA IN THE MICROBIOTA OF RIVER SLUDGE

Introduction. Bioaugmentation is an in situ bioremediation approach, which implies the introduction of a population of microorganisms with certain biodegrading abilities. Acrylamide is a biodegradable toxic substance. Our goal was to assess the survival of allochthonous bacterial cultures Alcaligenes faecalis 2 and Acinetobacter guillouiae 11h when introduced into river sludge and the efficiency of acrylamide decomposition by sludge with introduced amidase-containing bacteria. Methods. The microbiota of sludge from small rivers of Perm Territory was inoculated with the biomass of strains A. faecalis 2 and A. guillouiae 11h, which have amidase activity. In a laboratory experiment, we studied the survival of these bacteria as well as the biodegrading ability of the microbiota in relation to acrylamide after 3 and 6 months of incubation at 5 and 25°C. The transformation of acrylamide was assessed by HPLC, the biodiversity of river sludge was assessed by the method of metagenomic sequencing of 16S rRNA genes. Results. Incubation of sludge at 25°C for 3–6 months deteriorates the biodegrading abilities of the microbiota in relation to acrylamide, and the transformation of this pollutant occurs only during the augmentation of the biomass of amidase-containing bacteria, with acinetobacteria having an advantage over bacteria of Alcaligenes sp. Upon incubation of sludge at 25°C, the phylogenetic diversity increases, and the proportion of representatives of the phyla Actinobacteria, Chloroflexi, Ignavibacteriae, Candidatus Saccharibacteria, Acidobacteria increases as well, while the phylum Proteobacteria accounts for most of the bacterial biota in all samples, and the phylum Firmicutes accounts for 10–30%. The presence of representatives of Alcaligenes sp. and Acinetobacter sp. was confirmed in the microbiota of bioaugmented sludge after 6 months of incubation at 25°C. When incubated at 5°C, the microbiota of native sludge is capable of degrading acrylamide, but at a rate several times lower than during bioaugmentation. After incubation of Danilikha River sludge with the introduced biomass of strains A. guillouiae 11h and A. faecalis 2 at 5°C for 6 months, the complete transformation of acrylamide was observed in 4 and 20 days, respectively, with native sludge — in 35 days.

Effect of Natural Polysaccharide Matrix-Based Selenium Nanocomposites on Phytophthora cactorum and Rhizospheric Microorganisms

We studied the effects of new chemically synthesized selenium (Se) nanocomposites (NCs) based on natural polysaccharide matrices arabinogalactan (AG), starch (ST), and kappa-carrageenan (CAR) on the viability of phytopathogen Phytophthora cactorum, rhizospheric bacteria, and potato productivity in the field experiment. Using transmission electron microscopy (TEM), it was shown that the nanocomposites contained nanoparticles varying from 20 to 180 nm in size depending on the type of NC. All three investigated NCs had a fungicidal effect even at the lowest tested concentrations of 50 µg/mL for Se/AG NC (3 µg/mL Se), 30 µg/mL for Se/ST NC (0.5 µg/mL Se), and 39 µg/mL for Se/CAR NC (1.4 µg/mL Se), including concentration of 0.000625% Se (6.25 µg/mL) in the final suspension, which was used to study Se NC effects on bacterial growth of the three common rhizospheric bacteria Acinetobacter guillouiae, Rhodococcus erythropolis and Pseudomonas oryzihabitans isolated from the rhizosphere of plants growing in the Irkutsk Region. The AG-based Se NC (Se/AG NC) and CAR-based Se NC (Se/CAR NC) exhibited the greatest inhibition of fungal growth up to 60% (at 300 µg/mL) and 49% (at 234 µg/mL), respectively. The safe use of Se NCs against phytopathogens requires them to be environmentally friendly without negative effects on rhizospheric microorganisms. The same concentration of 0.000625% Se (6.25 µg/mL) in the final suspension of all three Se NCs (which corresponds to 105.57 µg/mL for Se/AG NC, 428.08 µg/mL for Se/ST NC and 170.30 µg/mL for Se/CAR NC) was used to study their effect on bacterial growth (bactericidal, bacteriostatic, and biofilm formation effects) of the three rhizospheric bacteria. Based on our earlier studies this concentration had an antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus that causes diseases of potato ring rot, but did not negatively affect the viability of potato plants at this concentration. In this study, using this concentration no bacteriostatic and bactericidal activity of all three Se NCs were found against Rhodococcus erythropolis based on the optical density of a bacterial suspension, agar diffusion, and intensity of biofilm formation, but Se/CAR and AG NCs inhibited the growth of Pseudomonas oryzihabitans. The cell growth was decrease by 15–30% during the entire observation period, but the stimulation of biofilm formation by this bacterium was observed for Se/CAR NC. Se/AG NC also had bacteriostatic and antibiofilm effects on the rhizospheric bacterium Acinetobacter guillouiae. There was a 2.5-fold decrease in bacterial growth and a 30% decrease in biofilm formation, but Se/CAR NC stimulated the growth of A. guillouiae. According to the results of the preliminary field test, an increase in potato productivity by an average of 30% was revealed after the pre-planting treatment of tubers by spraying them with Se/AG and Se/CAR NCs with the same concentration of Se of 0.000625% (6.25 µg/mL) in a final suspension. The obtained and previously published results on the positive effect of natural matrix-based Se NCs on plants open up prospects for further investigation of their effects on rhizosphere bacteria and resistance of cultivated plants to stress factors.

Las rizobacterias halófilas mantienen la calidad forrajera de Moringa oleifera cultivada en sustrato salino

Para obtener un incremento en la producción forrajera de Moringa oleifera Lam. y de buena calidad se puede combinar el uso de compost a base de estiércol bovino y la inoculación de biofertilizantes a base de rizobacterias promotores del crecimiento vegetal (PGPR). La evaluación de esta producción se realizó en invernadero en Torreón, Coahuila, México. Se utilizó compost de estiércol bovino como sustrato (compost 50%, arena 40% y perlita 10%). Se programaron tres inoculaciones al árbol (a los 40, 74 y 152 días después de la siembra) con cuatro cepas de PGPR, los siguientes fueron los tratamientos T1: Bacillus paralicheniformis, T2: Acinetobacter guillouiae, T3: Aeromonas caviae, T4: Pseudomonas lini y Testigo: Sin bacteria, las cepas provenientes de la Poza Salada, Valle de Sobaco, Coahuila, México. Se realizaron tres cosechas en el ciclo verano-otoño-invierno 2016-2017. Se evaluaron variables agronómicas y bromatológicas para determinar la producción y calidad del follaje del árbol. Las cepas Pseudomonas lini y Bacillus paralicheniformis proporcionaron una respuesta positiva en el desarrollo de M. oleifera forrajera en el período de verano-otoño, incrementando la altura en las primeras semanas de desarrollo y proporcionando diámetros más gruesos y firmes. El rendimiento y las variables bromatológicas no presentaron diferencia entre los tratamientos, sin embargo, se produjo un forraje de buena calidad. En promedio las hojas presentaron el 13.56 % de cenizas, 70.15 % de total de nutrientes digestibles, 93.16 % de digestibilidad in vitro de la materia seca, 19.72 % de fibra detergente neutra, 25.35 % de fibra detergente ácida y 24.15 % de proteína cruda.