Serratia Sp Research Articles

Heterologous expression, kinetic characterization and molecular modeling of a new sn-1,3-regioselective triacylglycerol lipase from Serratia sp. W3

A recombinant Serratia sp. W3 lipase (rSmL) was expressed in E. coli and purified to homogeneity. The kinetic properties, regio-selectivity, and interfacial performances of rSmL were compared with those of the native lipase (nSmL). rSmL has a molecular mass of 67 kDa and a specific activity of 3530 U mg−1 which is around 12-fold higher than that of nSmL (300 U mg−1) when using olive oil as the substrate. Both rSmL and nSmL were able to hydrolyze the ester bond at the sn-1 and sn-3 positions but exhibited a clear regio-preference towards the sn-3 position of the surface-coated triglycerides (TG), which were esterified with α-eleostearic acid at the sn-1/3 position or dicaprin isomers spread as monomolecular films. Molecular modeling and docking of TG into the active site of rSmL indicated that this regio-preference may be due to steric hindrance, created by the residues Ile308 and Trp311, with distances between the sn-1 reactive carbon and the catalytic Serine residue ranging from 3.15 to 5.47 Å. In contrast, the sn-3 positioning within the enzyme catalytic pocket resulted in shorter distances, ranging from 2.79 to 4.15 Å, therefore facilitating the hydrolysis at the sn-3 position.

Characterisation of hydrocarbon degradation, biosurfactant production, and biofilm formation in Serratia sp. Tan611: a new strain isolated from industrially contaminated environment in Algeria

A novel bacterial strain was isolated from industrially contaminated waste water. In the presence of crude oil, this strain was shown to reduce the rate of total petroleum hydrocarbons (TPH) up to 97.10% in 24h. This bacterium was subsequently identified by 16S rRNA gene sequence analysisand affiliated to the Serratia genus by the RDP classifier. Its genome was sequenced and annotated, and genes coding for catechol 1,2 dioxygenase and naphthalene 1,2-dioxygenase system involved in aromatic hydrocarbon catabolism, and LadA-type monooxygenases involved in alkane degradation, were identified. Gas Chromatography-Mass Spectrometry (GC-MS) analysis of crude oil after biological treatment showed that Serratia sp. Tan611 strain was able to degrade n-alkanes (from C13 to C25). This bacterium was also shown to produce a biosurfactant, the emulsification index (E24) reaching 43.47% and 65.22%, against vegetable and crude oil, respectively. Finally, the formation of a biofilm was increased in the presence of crude oil. These observations make Serratia sp. Tan611 a good candidate for hydrocarbon bioremediation.

Inoculation with Rhizobacteria Enhanced Tolerance of Tomato (Solanum lycopersicum L.) Plants in Response to Cadmium Stress

In this study, cadmium (Cd)-tolerant bacteria Serratia sp. D23 (D23) and Sphingomonas sp. D36 (D36) were isolated from Cd-contaminated rhizospheric soil. Both strains have indole-3-acetic acid production, phosphate solubilization and siderophores production ability. A hydroponic experiment was performed to evaluate the effect of D23 and D36 on Cd toxicity and Cd content in tomato plants. The results indicated that under Cd-stressed condition, D23 and D36 inoculation increased photosynthetic pigment content in tomato leaves and decreased malonyldialdehyde level in tomato roots (p < 0.05). Both strains could alleviate Cd-induced inhibition of dry mass accumulation, D23 inoculation increased the root and leaf dry mass by 44.95% and 99.13%, while D36 treatment increased the root and leaf dry mass by 41.56% and 46.81%, respectively. Besides, D23 treatment reduced the Cd content in tomato root by 46.70%, and D36 inoculation reduced the Cd content in root and leaf by and 27.63% and 35.41%. Moreover, the expression of stress-related genes, including Hsp90, MT2 and Nramp3 were enhanced by bacterial inoculation. The subcellular localization of Cd and the activity of antioxidant enzyme were also influenced by D23 and D36 colonization. Taken together, rhizobacteria D23 and D36 could alleviate Cd toxicity and reduce Cd concentration in tomato plants via alleviating oxidative stress, modulating Cd subcellular localization and upregulating stress-related gene expression. This study provides evidence of enhancing Cd tolerance in tomato plants via rhizosphere bacteria and will be helpful to establish bacterial-assisted approach for alleviating heavy metal toxicity in plants.

Evaluation of carcinogenic activities and sperm abnormalities of Gram-negative bacterial metabolites isolated from cancer patients after subcutaneous injection in albino rats.

Microbial pathogens drive tumorigenesis in 20% of cancer cases, so the present study is aimed to evaluate the carcinogenic activities, sperm abnormalities and other dangerous effects of the subcutaneous injection of extracts obtained from various clinical Gram-negative bacteria derived from cancer patients using albino rats. We isolated, identified and extracted of their secondary metabolites of carbapenem resistant Gram-negative bacteria derived from cancer patients. Various methods have been used to determine hepatotoxicity, nephrotoxicity, tumorigenesis, inflammatory and sperm abnormalities in the albino rats injected with extracts. In comparison with the normal animals group, all extracts induced hepatotoxicity which was evidenced by the significant elevation in the activity of the serum alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase and alkaline phosphatase; also, nephrotoxicity that was indicated through the marked increase in the serum urea and creatinine levels; tumorigenesis was achieved from the sharp elevation in serum levels of alpha fetoprotein, carcinoembryonic antigen and lactate dehydrogenase values as tumor markers; as well as severe inflammatory characteristics were monitored from the marked raise of tumor necrosis factor alpha and interleukin-1beta. Furthermore, the proportion of micronuclei in polychromatic erythrocytes and sperm abnormalities were statistically significant in all groups compared to control group. Various kinds of head abnormalities and coiled tail were noted. Histopathological examination of hepatic tissue came in line with the biochemical and cytological findings. It could conclude that the extracts of Serratia sp. Esraa 1, Stenotrophomonas sp. Esraa 2, Acinetobacter sp. Esraa 3, Escherichia sp. Esraa 4 and Pseudomonas sp. Esraa 5 were able to initiate cytotoxicity and tumorigenesis in rats.

Identification of a Pb-Resistant Acetochlor-Degrading Bacterium for Bioremediation of Soils Contaminated with Herbicides

Acetochlor, a commonly used herbicide, and Pb are two important soil contaminants often found to co-occur. The cytotoxic effects of heavy metals like Pb considerably reduce the efficacy of microbial bioremediation steps undertaken to remove chemical contaminants from soil. This necessitates the identification of heavy metal-tolerant microbial strains that can degrade chemical pollutants. In the present study, a Pb-resistant acetochlor-degrading bacterial strain belonging to the Serratia genus was isolated. We found that Serratia sp. QSxin4 could use acetochlor as the sole carbon source and grow well when incubated in a minimal medium containing 500 mg/L acetochlor and 200 mg/L Pb. QSxin4 could degrade acetochlor from 500 to about 4.5 mg/L within 48 h, with the maximum degradation rate of 12 ± 0.1 mg mL−1 h−1. GC-MS analysis showed that the bacterial strain could deoxyalkylate acetochlor to produce 2-ethyl-6-methyl-N-methyl-α-chloroacetanilide. Germination studies carried out with Eragrostis pilosa seeds, using soil containing 25 mg/kg acetochlor and 400 mg/kg Pb, revealed that QSxin4 could markedly reduce the toxic effects of acetochlor on seed germination by degrading acetochlor to a less toxic compound. Our findings indicate that QSxin4 can be used for bioremediation of acetochlor-contaminated soil contaminated with high concentrations of Pb.

The Rcs stress response inversely controls surface and CRISPR-Cas adaptive immunity to discriminate plasmids and phages.

Bacteria harbour multiple innate defences and adaptive CRISPR-Cas systems that provide immunity against bacteriophages and mobile genetic elements. Although some bacteria modulate defences in response to population density, stress and metabolic state, a lack of high-throughput methods to systematically reveal regulators has hampered efforts to understand when and how immune strategies are deployed. We developed a robust approach called SorTn-seq, which combines saturation transposon mutagenesis, fluorescence-activated cell sorting and deep sequencing to characterize regulatory networks controlling CRISPR-Cas immunity in Serratia sp. ATCC 39006. We applied our technology to assess csm gene expression for ~300,000 mutants and uncovered multiple pathways regulating type III-A CRISPR-Cas expression. Mutation of igaA or mdoG activated the Rcs outer-membrane stress response, eliciting cell-surface-based innate immunity against diverse phages via the transcriptional regulators RcsB and RcsA. Activation of this Rcs phosphorelay concomitantly attenuated adaptive immunity by three distinct type I and III CRISPR-Cas systems. Rcs-mediated repression of CRISPR-Cas defence enabled increased acquisition and retention of plasmids. Dual downregulation of cell-surface receptors and adaptive immunity in response to stress by the Rcs pathway enables protection from phage infection without preventing the uptake of plasmids that may harbour beneficial traits.

Assessment of Physicochemical and Microbial Suitability of Some Selected Surface Water around Ile?Ife Southwest Nigeria for Irrigation

This study investigated the physicochemical parameters as well as the microbial quality of certain water bodies used for irrigation purposes in Ife East and Ife Central Local Government Areas of Osun State, Nigeria. Physicochemical parameters of samples were measured following standard methods. The identity and population of autochthonous bacteria were determined using standard microbiological methods between November 2018 and March 2019. The physicochemical parameters assessed in the irrigation water samples revealed that pH values of irrigation water sampled falls between 7.06 ± 0.08–8.40 ± 0.12, mean value of Total Dissolved Solid (TDS) ranges between 104.00 ± 1.41 and 461.3 ± 1.78 ppm while temperature was around 31.83 ± 0.51°C. Turbidity of the irrigation water sampled exceeded the recommended (˂5 NTU) range. Heterotrophic plate count, Total Coliform and Feacal Coliform count were found to be relatively high (2.80 ± 0.04–7.28 ± 0.28 Log10 cfu/ml) and no significant difference (p-values˃0.05) was observed in their mean values. A total of 12-13 bacteria species were found in Ife Central and Ife East respectively. These bacteria include Aeromonas sp, Aeromonas hydrophilla Citrobacter sp, E coli; Enterococcus sp, Klebsiella sp, Proteus sp, Pseudomonas sp, Salmonella sp, Serratia sp, Shigella sp, Staphylococcus sp and Vibrio sp. This study concludes that pH and TDS were within the acceptable limits while temperature exceeded the standard in some months. The presence of pathogenic bacteria suggests that irrigation water could be a major source of transmission of waterborne diseases and consequently detrimental to human health.

Cellulolytic bacterium characterization and genome functional analysis: An attempt to lay the foundation for waste management

Lignocellulosic waste has offered a cost-effective and food security-wise substrate for the generation of biofuels and value-added products. Here, whole-genome sequencing and comparative genomic analyses were performed for Serratia sp. AXJ-M. The results showed that strain AXJ-M contained a high proportion of strain-specific genes related to carbohydrate metabolism. Furthermore, the genetic basis of strain AXJ-M for efficient degradation of cellulose was identified. Cellulase activity tests revealed strong cellulose degradation ability and cellulase activities in strain AXJ-M. mRNA expression indicated that GH1, GH3 and GH8 might determine the strain’s cellulose degradation ability. The SWISS-MODEL and Ramachandran Plot were used to predict and evaluate the 3D structure, respectively. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometer (GC–MS) were used to analyze the cellulose degradation products. Further research is needed to elucidate the cellulose degradation mechanism and to develop industrial applications for lignocellulosic biomass degradation and waste management.

Serratia sp. CP-13 alleviates Cd toxicity by morpho-physio-biochemical improvements, antioxidative potential and diminished Cd uptake in Zea mays L. cultivars differing in Cd tolerance

Cadmium (Cd) is highly toxic for plant metabolic processes even in low concentration due to higher retention rates, longer half-life and non-biodegradable nature. The current study was designed to assess the bioremediation potential of Cd tolerant PGPR, Serratia sp. CP-13 together with two differentially Cd tolerant maize cultivars (MMRI-Yellow, Sahiwal-2002) selected amongst ten cultivars after screening. The maize cultivars were grown under different Cd treatments (0, 6, 12, 18, 24, 30 µM) in Petri plates both with and without Serratia sp. CP-13 inoculation. Treated plants were analyzed for their biomass accumulation, chlorophylls, carotenoids, proline, anthocyanin, protein, malondialdehyde (MDA), H2O2 as well as for antioxidants (POD, SOD, CAT) and mineral elements (Ca, Mg, Zn, K, Fe, Na, Cd). The maize cultivar MMRI-Yellow (tolerant) and Sahiwal-2002 (sensitive) exhibited significant reduction in leaf area, nutrient contents, plant biomass, activity of antioxidants, total proteins, photosynthetic pigments as well as flavonoids with increased production of H2O2, proline, MDA and relative membrane permeability (RMP) under Cd stress. However, this reduction was cultivar specific and recorded higher in cv. Sahiwal-2002 as compared to MMRI-Yellow. Application of Serratia sp. CP-13 significantly augmented plant biomass, photosynthetic pigments, antioxidative machinery, as well as flavonoids and proline while diminishing H2O2, RMP MDA production even under Cd stress in studied cultivars. Furthermore, CP-13 inoculation assisted the Cd stressed plants to sustain an optimal level of essential nutrients (Ca, Mg, Zn, K, Fe) except for Na and Cd which responded antagonistically. It was inferred that both inoculated maize cultivars exhibited better health and metabolism but substantial Cd tolerance was acquired by the sensitive cv. Sahiwal-2002 than the tolerant cv. MMRI-Yellow under applied Cd regimes. Furthermore, studied maize cultivars depicted maximum Cd tolerance in order of 30 < 24 < 18 < 12 < 6 < 0 µM Cd treatments under Serratia sp. CP-13 inoculation. Findings of current work highlighted the importance of Serratia sp. CP-13 and its inoculation impact on morpho-physio-biochemical attributes of maize growth under Cd dominant environment, which is likely an addition towards efficient approaches for bacterially-assisted Cd bioremediation and minimal Cd retention in edible plant parts.

Ambigols from the Cyanobacterium Fischerella ambigua Increase Prodigiosin Production in Serratia spp.

When a library of 573 cyanobacteria extracts was screened for inhibition of the quorum sensing regulated prodigiosin production of Serratia marcescens, an extract of the cyanobacterium Fischerella ambigua (Näg.) Gomont 108b was found to drastically increase prodigiosin production. Bioactivity-guided isolation of the active compounds resulted in the two new natural products ambigol D and E along with the known ambigols A and C. Ambigol C treatment increased prodiginine production of Serratia sp. ATCC 39006 (S39006) by a factor of 10, while ambigols A and D were found to have antibiotic activity against this strain. The RNA-Seq of S39006 treated with ambigol C and subsequent differential gene expression and functional enrichment analyses indicated a significant downregulation of genes associated with the translation machinery and fatty acid biosynthesis in Serratia, as well as increased expression of genes related to the uptake of l-proline. These results suggest that the ambigols increase prodiginine production in S39006 not by activating the SmaIR quorum sensing system but possibly by increasing the precursor supply of l-proline and malonyl-CoA.

Evaluation of bioremediation and detoxification potentiality for papermaking black liquor by a new isolated thermophilic and alkali-tolerant Serratia sp. AXJ-M

There is a great need for efficiently treating papermaking black liquor because it can seriously pollute both soil and water ecosystems. In this study, the Plackett–Burman (PB) experimental design combined with response surface methodology (RSM) was used for improving the biodegradation efficiency of lignin by a new isolated thermophilic and alkali-tolerant strain Serratia sp. AXJ-M, and the results showed that a biodegradation efficiency of 70.5% was achieved under optimal culture conditions. The bacterium with ligninolytic activities significantly decreased target the parameters (color 80%, lignin 60%, phenol 95%, BOD 80% and COD 80%). The control and treated samples were analyzed by gas chromatography-mass spectrometer (GC-MS), which showed that the concentrations of a majority of low-molecular-weight compounds were decreased after biological treatment. Furthermore, toxicological, genotoxicity and phytotoxicity studies have supported the detoxification by the bacterium of black liquor. Finally, the genome sequence of the thermophilic, alkali-tolerant and lignin-degrading bacterium AXJ-M was completed, and the genetic basis of the thermophilic and alkali-resistant properties of AXJ-M was preliminarily revealed. The dyp-type peroxidase was first reported to have the potential to catalyze lignin degradation structurally. These findings suggest that Serratia sp. AXJ-M may be potentially useful for bioremediation applications for papermaking black liquor.

Production and purification of bacteriocin from Leuconostoc lactis SM 2 strain

Abstract Food bio-preservation can be accomplished by antimicrobial peptides, the bacteriocins. In the present study, bacteriocin producing bacteria were screened and isolated from various food sources. Amongst them, Leuconostoc lactis SM2 was found to produce bacteriocin, with maximum antimicrobial activity against target bacterial strains. The bacteriocin was produced in shake flasks for 24 h at pH 7.0 and temperature 37 °C. The bacteriocin was purified through subsequent steps of salting out and size exclusion chromatography thus achieving a purity of 34.75%. Elution spectrum of HPLC revealed the leucocin nature of the bacteriocin. Although leucocin showed antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas putida, Klebsiella and Serratia sp, but the highest towards E. coli upon Lactobacillus MRS agar medium. This affinity was confirmed by molecular docking studies, indicating greater binding energy towards E.coli (−123.22 kcal/mol) than S. aureus (−64.63 kcal/mol). The antimicrobial effect was most prominent if the pure leucocin was added at the lag phase of growth of the target organism. Failure of revival by the bacteriocin treated second generation cells revealed the bactericidal, not bacteriostatic nature of the protein. Sustained skin texture, freshness of seeds with characteristic sharp smell in bacteriocin treated chillies indicated the applicability of leucocin for food preservation.

Identification, Characterization, and Genomic Analysis of Novel Serratia Temperate Phages from a Gold Mine.

Bacteria of the genus Serratia inhabit a variety of ecological niches like water, soil, and the bodies of animals, and have a wide range of lifestyles. Currently, the complete genome sequences of 25 Serratia phages are available in the NCBI database. All of them were isolated from nutrient-rich environments like sewage, with the use of clinical Serratia strains as hosts. In this study, we identified a novel Serratia myovirus named vB_SspM_BZS1. Both the phage and its host Serratia sp. OS31 were isolated from the same oligotrophic environment, namely, an abandoned gold mine (Zloty Stok, Poland). The BZS1 phage was thoroughly characterized here in terms of its genomics, morphology, and infection kinetics. We also demonstrated that Serratia sp. OS31 was lysogenized by mitomycin-inducible siphovirus vB_SspS_OS31. Comparative analyses revealed that vB_SspM_BZS1 and vB_SspS_OS31 were remote from the known Serratia phages. Moreover, vB_SspM_BZS1 was only distantly related to other viruses. However, we discovered similar prophage sequences in genomes of various bacteria here. Additionally, a protein-based similarity network showed a high diversity of Serratia phages in general, as they were scattered across nineteen different clusters. In summary, this work broadened our knowledge on the diverse relationships of Serratia phages.

High-throughput sequencing analysis of the bacterial community for assessing the differences in extraction methods of bacteria separation from chilled pork

The aim of this study was to apply high-throughput sequencing to analyse the differences among three extraction methods (A—direct separation of bacteria, B—the precipitation of bacterial colonies at 37 °C, and C—the precipitation of bacterial colonies at 6.5 °C) of bacteria separation from chilled pork on day 0, 4 and 8. Results of PCA and Venn plot indicated that three methods of bacteria separation from pork resulted in different bacterial communities. At the beginning of storage, group A showed higher numbers of OTUs (Operational Taxonomic Units) and species of bacteria in the pork. Acinetobacter sp. and Myroides sp. were dominant at the beginning of storage and then Photobacterium sp. and Pseudomonas sp. dominated on day 4 and 8. For group B, the predominant bacteria were Aeromonas sp., followed by Kurthia sp. and Enterobacter sp. on day 0 and 4. Group C showed dynamic changes in the bacterial community during storage, with an increase in the relative abundances of Pseudomonas sp., Myroides sp. and Shewanella sp. and a decrease in Aeromonas sp., Acinetobacter sp. and Serratia sp. These results provide scientific information to understand bacterial communities by different bacterial extraction methods from meat.

Is Long-Term Heavy Metal Exposure Driving Carriage of Antibiotic Resistance in Environmental Opportunistic Pathogens: A Comprehensive Phenomic and Genomic Assessment Using Serratia sp. SRS-8-S-2018.

The carriage of both, heavy metal and antibiotic resistance appears to be a common trait in bacterial communities native to long-term contaminated habitats, including the Savannah River Site (SRS). There is widespread soil contamination at the SRS; a United States Department of Energy (DOE) facility with long-term contamination from past industrial and nuclear weapons production activities. To further evaluate the genomic and metabolic traits that underpin metal and antibiotic resistance, a robust mercury (Hg) and uranium (U)-resistant strain- SRS-8-S-2018, was isolated. Minimum inhibitory concentration of this strain revealed resistance to Hg (10 μg/ml) and U (5 mM), the two main heavy metal contaminants at the SRS. Metabolic assessment of strain SRS-8-S-2018 using Biolog metabolic fingerprinting analysis revealed preference for carbohydrate utilization followed by polymers, amino acids, carboxy acids, and esters; this physiological activity diminished when Hg stress was provided at 1 and 3 μg/ml and completely ceased at 5 μg/ml Hg, indicating that continued release of Hg will have negative metabolic impacts to even those microorganisms that possess high resistance ability. Development of antibiotic resistance in strain SRS-8-S-2018 was evaluated at a functional level using phenomics, which confirmed broad resistance against 70.8% of the 48 antibiotics tested. Evolutionary and adaptive traits of strain SRS-8-S-2018 were further assessed using genomics, which revealed the strain to taxonomically affiliate with Serratia marcescens species, possessing a genome size of 5,323,630 bp, 5,261 proteins (CDS), 55 genes for transfer RNA (tRNA), and an average G + C content of 59.48. Comparative genomics with closest taxonomic relatives revealed 360 distinct genes in SRS-8-S-2018, with multiple functions related to both, antibiotic and heavy metal resistance, which likely facilitates the strain’s survival in a metalliferous soil habitat. Comparisons drawn between the environmentally isolated Serratia SRS-8-S-2018 with 31 other strains revealed a closer functional association with medically relevant isolates suggesting that propensity of environmental Serratia isolates in acquiring virulence traits, as a function of long-term exposure to heavy metals, which is facilitating development, recruitment and proliferation of not only metal resistant genes (MRGs) but antibiotic resistant genes (ARGs), which can potentially trigger future bacterial pathogen outbreaks emanating from contaminated environmental habitats.

Cloning and expression of pigC gene in Escherichia coli

Prodigiosin (Pg), which is particularly of interest because of anticancer and antimicrobial activities, can be produced through the PigC-catalyzed condensation reaction of 4-methoxy-2, 2’-bipyrrole-5-carboxyaldehyde (MBC) and 2-methyl-3-amylpyrrole (MAP). Therefore, the PigC protein plays an important role in prodigiosin biosynthetic pathway. However, studies related to PigC protein have not been carried out in Vietnam yet. In this work, the pigC gene was cloned and expressed in Escherichia coli DH10B and BL21 (DE3), respectively. Using PCR and universal primers, we amplified a fragment of 3 kb covering entire coding region of the pigC gene from Serratia sp. strain M5. The pigC gene was inserted into pJET1.2 vector, and then transformed into E. coli DH10B. The sequence of a recombinant vector pJET1.2/pigC was evaluated by using whole colony PCR amplification. Sequence alignment results revealed that the obtained pigC gene possesses 71.5% and 75.4% of nucleotide identity in comparison with two strains, Serratia 39006 and Serratia sp. AS9 published in GenBank with their respective accession numbers of AJ833001 and CP002773. The recombinant vector pJET1.2/pigC was used to reamplify pigC, and the acquired amplicon was inserted into pET22b vector at the site of HindIII and XhoI. The clone E. coli BL21 (DE3) containing recombinant vector pET22b/pigC was expressed in the auto-induced medium. The presence of PigC protein in the lysate was identified as a 100 kDa band through Western Blot analysis using anti his-tag antibody. Afterward, the PigC protein was purified by Ni-NTA column, and its expression level was quantified through SDS-PAGE analysis. The results of our study provide a potential material for producing prodigiosin from recombinant protein in Vietnam.

Chromium metabolism characteristics of coexpression of ChrA and ChrT gene

ObjectiveSerratia sp. S2 is a wild strain with chromium resistance and reduction ability. Chromium(VI) metabolic-protein-coding gene ChrA and ChrT were cloned from Serratia sp. S2, and ligated with prokaryotic expression vectors pET-28a (+) and transformed into E. coli BL21 to construct ChrA, ChrT and ChrAT engineered bacteria. By studying the characteristics of Cr(VI) metabolism in engineered bacteria, the function and mechanism of the sole expression and coexpression of ChrA and ChrT genes were studied. MethodsUsing Serratia sp. S2 genome as template, ChrA and ChrT genes were amplified by PCR, and prokaryotic expression vectors was ligated to form the recombinant plasmid pET-28a (+)-ChrA, pET-28a (+)-ChrT and pET-28a (+)-ChrAT, and transformed into E. coli BL21 to construct ChrA, ChrT, ChrAT engineered bacteria. The growth curve, tolerance, and reduction of Cr(VI), the distribution of intracellular and extracellular Cr, activity of chromium reductase and intracellular oxidative stress in engineered bacteria were measured to explore the metabolic characteristics of Cr(VI) in ChrA, ChrT, ChrAT engineered bacteria. ResultsChrA, ChrT and ChrAT engineered bacteria were successfully constructed by gene recombination technology. The tolerance to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrA > ChrT > Control (P < 0.05), and the reduction ability to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrT > ChrA (P < 0.05). The chromium distribution experiments confirmed that Cr(VI) and Cr(III) were the main valence states. Effect of electron donors on chromium reductase activity was NADPH > NADH > non-NAD(P)H (P < 0.05). The activity of chromium reductase increased significantly with NAD(P)H (P < 0.05). The Glutathione and NPSH (Non-protein Sulfhydryl) levels of ChrA, ChrAT engineered bacteria increased significantly (P < 0.05) under the condition of Cr(VI), but there was no significant difference in the indexes of ChrT engineered bacteria (P > 0.05). ConclusionChrAT engineered bacteria possesses resistance and reduction abilities of Cr(VI). ChrA protein endows the strain with the ability to resist Cr(VI). ChrT protein reduces Cr(VI) to Cr(III) by using NAD(P)H as electronic donor. The reduction process promotes the production of GSH, GSSG and NPSH to maintain the intracellular reduction state, which further improves the Cr(VI) tolerance and reduction ability of ChrAT engineered bacteria.

An appraisal of the drinking water quality of groundwater sources in Ogbomoso, Oyo state, Nigeria

A total of one hundred and twenty-two water samples were obtained from hand-dug wells and boreholes in Ogbomoso metropolis, Oyo State, Nigeria. Physico-chemical, most probable number technique, direct culture methods, and water quality index were used to assess the drinking water quality in this region. Some of the physicochemical parameters were within the acceptable limits, with the exemption of conductivity (940 μscm−1), total dissolved solids (1120 mgL−1) total hardness (404 mg CaCO3L−1), and Cl− ion (220 mg/L). Escherichia coli, Klebsiella sp, Staphylococcus aureus, Shigella dysenteriae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella sp, and Serratia sp are some of the isolates obtained from the water samples. Total coliform count in the well water samples was higher than those from boreholes, with E. coli having up to 180 and 45 CFU/mL for well and borehole water samples respectively. The calculated water quality index indicated poor drinking water quality. Some of the isolates were resistant to nothing less than three antibiotics and a maximum of ten antibiotics. All approaches used for assessing the water samples emphasize the need for improvement in water quality to safeguard public health. Drinking water from hand-dug wells and boreholes in this region requires treatment by chlorination, filtration, and boiling before consumption. Government bodies saddled with environmental and health responsibilities in the region should provide a potable water supply.

Biodegradation of CP/TCP by a constructed microbial consortium after comparative bacterial community analysis of long-term CP domesticated activated sludge

The objective of this study was to construct a microbial consortium for effective biodegradation of chlorpyrifos (CP) and its hydrolysis product, 3,5,6-Trichloro-2-pyridinol (TCP). A activated sludge from an organophosphorus pesticide factory was domesticated under long-term (20 weeks) CP stress, and the dynamic change in bacterial communities was analyzed by high-throughput sequencing. Then, a microbial consortium MC-BSPK was constructed of Bacillus sp. MC-B, Serratia sp. MC-S, Pseudomonas sp. MC-P, and Klebsiella sp. MC-K, which were significantly enriched during the domestication process. The biodegradation capacities of the microbial consortium MC-BSPK reached 100% for CP within 9 days and 88.61% for TCP within 15 days under the optimized degradation conditions (pH 8.0 and 31 °C). High-performance liquid chromatography (HPLC) revealed that CP could be degraded by the microbial consortium MC-BSPK into TCP, probably through hydrolysis of the P–O ester bond, and further degraded into other small molecules. A bioassay revealed that the virulence of CP toward Drosophila melanogaster W1118 was clearly reduced by the microbial consortium MC-BSPK biodegradation. Thus, the easily constructed microbial consortium MC-BSPK with high CP/TCP degradation capacities has the potential for application in pesticide-contaminated bioremediation.

Motility and biofilm production involved in the interaction of phosphate solubilizing endophytic strains with peanut, maize and soybean plants

Endophytic plant growth promoting bacteria are of great interest since the ability to colonize the internal tissues of plants gives it an adaptive advantage. To confer any beneficial effect on the plant, bacteria must present a successful colonization and thus be competent in the rhizosphere and finally infect internal tissues. In this sense, bacterial motility is an essential property involved in plant-microorganism interaction where bacteria can colonize the root and at the same time form biofilms. Within plant beneficial bacteria those that present phosphate solubilizing activity are of great interest due to the contribution of phosphorus to plants. The objective of this work was to evaluate the motility and biofilm formation properties of the strains Serratia sp. S119 and Enterobacter sp. J49 growing in the presence of peanut, maize and soybean root exudates. Results obtained indicated that both strains have flagella, possess swimming, swarming and twitching motilities and showed differential chemotactic attraction against root exudates. In addition, the strains under study showed the ability to form biofilms, being this ability greater in minimal media, in which a greater decrease was also seen by the addition of root exudates in the first hours of growth. The changes produced by the addition of root exudates in the chemotaxis and biofilm formation of the strains suggests that compounds released by the plants are detected by these bacteria and could be part of the molecular dialogue involved in their interaction with the roots of plant.