Simultaneous aerobic nitrogen and phosphate removal capability of novel salt-tolerant strain, Pseudomonas mendocina A4: Characterization, mechanism and application potential.

A salt-tolerant strain, Pseudomonas mendocina A4, was isolated from brackish-water ponds showing simultaneous heterotrophic nitrification-aerobic denitrification and phosphorus removal capability. The optimal conditions for nitrogen and phosphate removal of strain A4 were pH 7-8, carbon/nitrogen ratio 10, phosphorus/nitrogen ratio 0.2, temperature 30 °C, and salinity range of 0-5 % using sodium succinate as the carbon source. The nitrogen and phosphate removal efficiencies were 96-100 % and 88-96 % within 24 h, respectively. The nitrogen and phosphate removal processes were matched with the modified Gompertz model, and the underlying mechanisms were confirmed by the activities of key metabolic enzymes. Under 10 % salinity, the immobilization technology was employed to enhance the nitrogen and phosphate removal efficiencies of strain A4, achieving 87 % and 76 %, respectively. These findings highlight the potential application of strain A4 in both freshwater and marine culture wastewater treatment.

Rapid simultaneous removal of nitrogen and phosphorous by a novel isolated Pseudomonas mendocina SCZ-2.

Nitrogen (N) and phosphorous (P) removal by a single bacterium could improve the biological reaction efficiency and reduce the operating cost and complexity in wastewater treatment plants (WWTPs). Here, an isolated strain was identified as Pseudomonas mendocina SCZ-2 and showed high performance of heterotrophic nitrification (HN) and aerobic denitrification (AD) without intermediate accumulation. During the AD process, the nitrate removal efficiency and rate reached a maximum of 100% and 47.70 mg/L/h, respectively, under optimal conditions of sodium citrate as carbon source, a carbon-to-nitrogen ratio of 10, a temperature of 35 °C, and shaking a speed of 200 rpm. Most importantly, the strain SCZ-2 could rapidly and simultaneously eliminate N and P with maximum NH4+-N, NO3--N, NO2--N, and PO43--P removal rates of 14.38, 17.77, 20.13 mg N/L/h, and 2.93 mg P/L/h, respectively. Both the N and P degradation curves matched well with the modified Gompertz model. Moreover, the amplification results of functional genes, whole genome sequencing, and enzyme activity tests provided theoretical support for simultaneous N and P removal pathways. This study deepens our understanding of the role of HN-AD bacteria and provides more options for simultaneous N and P removal from actual sewage.

Arsenic Resistance Mechanisms in Pseudomonas mendocina SMSKVR-3 Strain Isolated from Khetri Copper Mines, Rajasthan, India.

An arsenic resistant bacteria SMSKVR-3 has been isolated from the rhizospheric soil of the metal-contaminated site of khetri copper mines situated in the Jhunjhunu district of Rajasthan, India. The strain showed homology with Pseudomonas mendocina strain ATCC 25411. This gram-negative isolate exhibited optimal growth in M9 minimal media with temperature and salt concentration as 30 °C and 0.25% (w/v), respectively, at pH 7.0. The similar growth pattern and SEM analysis of this strain exposed to M9 minimal media alone, M9 media supplemented with 300 mM arsenate [As(V)] or M9 media supplemented with 1.34 mM arsenite [As(III)] indicate the existence of the strong arsenic resistance mechanism. The isolate was able to produce siderophores and was able to reduce As(V) to As(III). A decrease in polyP concentration from 354.8 µg/1010 CFU mL-1 at 0 h to 0.043 µg/1010 CFU mL-1 at 8 h incubation with As(V) was in correlation with the change in intracellular As(V) concentration (116.98 mg L-1/1010 cells at 0 h to 88.65 mg L-1/1010 at 8 h) with time. This shows the possible role of polyP bodies in the regulation of As(V) concentration inside the cell. The presence of arsC gene in P.mendocina SMSKVR-3 was confirmed by the PCR amplification of arsC gene. The BLAST analysis of the sequenced gene represented 98.59% identity with the P. mendocina S5.2 arsenate reductase. These results indicate that the observed arsenic resistance in SMSKVR-3 is due to a combination of siderophore production, the transformation of As(V) to As(III) by arsenate reductase, multi-drug efflux pump, and polyP bodies mediated metal resistance mechanism.

4-4' Diaponeurosporenic Acid, the C30 Carotenoid Pigment in Endophytic Pseudomonas Mendocina with Squalene Cyclase Activity.

Even though organisms with squalene hopene cyclase activity involved in hopanoid synthesis has been reported earlier, their existence along with carotenoid synthesis is rarely reported. Here, we report the existence of hopanoid and C30 carotenoid biosynthetic pathway in Pseudomonas mendocina, the squalene hopene cyclase producing endophyte of the medicinal plant Murraya koenigii. The enzyme squalene hopene cyclase from Pseudomonas mendocina is involved in the synthesis of dehydrosqualene-mediated alternate pathway for carotenoid biosynthesis. The hopanoids are involved in membrane stability and integrity, and the carotene chromophores are involved in the photo protection of the cell. The orange-colored C30 carotenoid pigment 4-4' diaponeurosporenic acid in the extracellular extract of Pseudomonas mendocina with squalene cyclase activity was detected by the combination of UV/Vis spectrometry, FTIR, and Mass Spectrometry. 4-4' diaponeurosporenic acid could be traced as the end product of the carotenoid pathway and belonged to the xanthophyll group of carotenoids.

Aerobic Biodegradation of OCDD by P. Mendocina NSYSU: Effectiveness and Gene Inducement Studies.

The goals of this study were to assess the effectiveness of (1) enhancing octachlorinated dibenzo-p-dioxin (OCDD) biodegradation under aerobic conditions by Pseudomonas mendocina NSYSU (P. Mendocina NSYSU) with the addition of lecithin, and (2) inducing OCDD ring-cleavage genes by pentachlorophenol (PCP) and OCDD addition. P. Mendocina NSYSU could biodegrade OCDD via aerobic cometabolism and lecithin was used as a primary substrate. Approximately 74 and 67% of OCDD biodegradation was observed after 60 days of incubation with lecithin and glucose supplement, respectively. Lecithin was also used as the solubilization additive resulting in OCDD solubilization and enhanced bioavailability of OCDD to P. Mendocina NSYSU. Two intradiol and extradiol ring-cleavage dioxygenase genes (Pmen_0474 and Pmen_2526) were identified from gene analyses. Gene concentration was significantly enhanced after the inducement by PCP and OCDD. Higher gene inducement efficiency was obtained using PCP as the inducer, and Pmen_2526 played a more important role in OCDD biodegradation.

Enhanced anaerobic biodegradation of OCDD-contaminated soils by Pseudomonas mendocina NSYSU: microcosm, pilot-scale, and gene studies.

In this study, microcosm and pilot-scale experiments were performed to investigate the capability and effectiveness of Pseudomonas mendocina NSYSU (P. mendocina NSYSU) on the bioremediation of octachlorodibenzo-p-dioxin (OCDD)-contaminated soils. The objectives were to evaluate the (1) characteristics of P. mendocina NSYSU, (2) feasibility of enhancing OCDD biodegradation with the addition of P. mendocina NSYSU and lecithin, and (3) variation in microbial diversity and genes responsible for the dechlorination of OCDD. P. mendocina NSYSU was inhibited when salinity was higher than 7%, and it could biodegrade OCDD under reductive dechlorinating conditions. Lecithin could serve as the solubilization agent causing the enhanced solubilization and dechlorination of OCDD. Up to 71 and 62% of OCDD could be degraded after 65 days of incubation under anaerobic conditions with and without the addition of lecithin, respectively. Decreased OCDD concentrations caused significant increase in microbial diversity. Results from the pilot-scale study show that up to 75% of OCDD could be degraded after a 2.5-month operational period with lecithin addition. Results from the gene analyses show that two genes encoding the extradiol/intradiol ring-cleavage dioxygenase and five genes encoding the hydrolase in P. mendocina NSYSU were identified and played important roles in OCDD degradation.

Differential effects of Pseudomonas mendocina and Glomus intraradices on lettuce plants physiological response and aquaporin PIP2 gene expression under elevated atmospheric CO2 and drought.

Arbuscular mycorrhizal (AM) symbiosis and plant-growth-promoting rhizobacterium (PGPR) can alleviate the effects of water stress in plants, but it is unknown whether these benefits can be maintained at elevated CO2. Therefore, we carried out a study where seedlings of Lactuca sativa were inoculated with the AM fungus (AMF) Glomus intraradices N.C. Schenk & G.S. Sm. or the PGPR Pseudomonas mendocina Palleroni and subjected to two levels of watering and two levels of atmospheric CO2 to ascertain their effects on plant physiological parameters and gene expression of one PIP aquaporin in roots. The inoculation with PGPR produced the greatest growth in lettuce plants under all assayed treatments as well as the highest foliar potassium concentration and leaf relative water content under elevated [CO2] and drought. However, under such conditions, the PIP2 gene expression remained almost unchanged. G. intraradices increased significantly the AMF colonization, foliar phosphorus concentration and leaf relative water content in plants grown under drought and elevated [CO2]. Under drought and elevated [CO2], the plants inoculated with G. intraradices showed enhanced expression of the PIP2 gene as compared to P. mendocina or control plants. Our results suggest that both microbial inoculation treatments could help to alleviate drought at elevated [CO2]. However, the PIP2 gene expression was increased only by the AMF but not by the PGPR under these conditions.

Treatment of waste gas containing monomethylamine in a biofilter enriched with Pseudomonas mendocina.

Waste gas containing monomethylamine (MMA) was treated in a biofilter packed with compost along with wood chips and enriched with Pseudomonas mendocina. The biofilter could remove MMA to the extent of more than 99% at a loading of 42.36 gm(-3)h(-1) with an empty bed retention time of 12s. At optimal operating conditions, the moisture content in the biofilter was maintained at around 45%. The biodegradative products of MMA were ammonia, nitrite, and nitrate.

Influence of carbon source on pyrimidine synthesis in Pseudomonas mendocina.

The effect of carbon source on the regulation of the de novo pyrimidine biosynthetic enzymes in the bacterium Pseudomonas mendocina was studied. When glucose was the carbon source, orotic acid supplementation of P. mendocina cells produced the greatest depression of aspartate transcarbamoylase, dihydroorotate dehydrogenase and orotate phosphoribosyltransferase activities while P. mendocina cells grown in the presence of uracil caused the maximal decrease in dihydroorotase and OMP decarboxylase activities. After the pyrimidine starvation of an orotate phosphoribosyltransferase mutant strain of P. mendocina grown on glucose, the pyrimidine biosynthetic pathway enzyme activities were generally diminished. With respect to pyrimidine starvation studies, the carbon source glucose appeared to lessen regulation at the level of enzyme synthesis compared to what has been observed when succinate served as the carbon source. The regulation of the pyrimidine biosynthetic pathway by carbon source in P. mendocina appeared to differ from how carbon source influenced the control of pyrimidine biosynthesis in the closely-related species Pseudomonas stutzeri.