Microbiol. Res., Volume 9, Issue 1 (June 2018) – 10 articles

RpfG is a member of a class of wide spread bacterial two-component regulators with an HD-GYP cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris pv. campestris (Xcc), RpfG together with the sensor kinase RpfC regulates the synthesis of a range of virulence factors as a response to the cell-cell Diffusible Signaling Factor (DSF). RpfG regulates many different virulence factors by divergent pathways. Physical interaction of RpfG with two diguanylate cyclase (GGDEF) domain proteins controls motility. This is a dynamic interaction that depends upon DSF signaling and involves the conserved GYP motif in the HD-GYP domain. Here we use synthetic peptide overlay technology and yeast two-hybrid analysis in conjunction with alanine substitution mutagenesis to define a motif within the GGDEF domain proteins required for interaction. We show that regulation of motility by the GGDEF domain proteins depends upon this motif. Furthermore, we show by Y2H that both GGDEF domain proteins bind a specific PilZ domain adaptor protein, and this interacts with the pilus motor proteins PilU and PiIT. The results support a model in which DSF signaling influences motility through the interaction of proteins that affect pilus action. The motif required for HD-GYP domain interaction is conserved in a number of GGDEF domain proteins, suggesting that regulation via interdomain interactions may be of broad relevance. Full article

Saffron is one of the most expensive spices in the world (20,000 €/kg) and this is due not only to the high demand for its various uses such as cooking, production of staining medicines, cosmetics etc., but also for the high costs of cultivation and production. Several studies have demonstrated that differences in saffron quality are mainly due to the methodology followed in the processing of stigmas, and environmental conditions independent of the origin. Some authors found phenotypic variations within cultivated saffron, but very limited genetic diversity. The reason for the very limited genetic diversity in cultivated saffron is explained by its asexual mode of reproduction (propagation). The aim of this study was to assess the antimicrobial activity of stigma saffron, which were tested against different bacteria strains. The results obtained from the antimicrobial activity study indicate that stigmas of C. sativus have some antimicrobial effect. Full article

The aims of this study were to investigate the antibiotics susceptibility, multidrug- resistant (MDR) frequency and the association of integrons with MDR among phylogenic groups of uropathogenic E. coli (UPEC). In total, 176 non-duplicated UPEC isolates were collected from urinary tract infections (UTIs) specimens. The disk diffusion method was performed for determination of antibiotic susceptibility patterns. Phylogenetic grouping and the presence of integron-associated genes (int) were detected by the PCR technique. A high frequency of resistance was observed to cotrimoxazole (96.9%), ampicillin (85%), trimethoprim (80.1%) and cefazolin (79.6%); and 140 isolates (79.5%) were MDR. Carbapenems and fosfomycin were the most effective antibiotics. The majority of isolates (60.8%) belonged to the phylogenic group B2. Integrons were detected in 135 (76.7%) of isolates and, class I was the most common (63.6%) class. MDR isolates were found to be significantly associated with class І integrons. These isolates were found to be closely associated with the phylogenic group D (82%), however, the presence of class І integrons was higher among MDR isolates of the phylogroup B1. This pattern is believed to be due to other mechanisms such as the overexpression of the efflux pumps. Our findings show a significant correlation between MDR and the presence of class І integron. We conclude that class 1 integron plays an important role in the development of MDR UPEC, especially among the phylogroup B1. Full article

Pomegranate is known for it's many health benefits. These benefits are due to the biological active compounds which are present in the pulp as well as in the peel of the pomegranate. The active compounds from the peel were obtained using cold percolation method using ethanol as solvent. Antibacterial activity of pomegranate peel extract (PPE) was studied on E. coli, E. coli NCIM 2065, Salmonella typhi, Salmonella paratyphi B, Pseudomonas aeruginosa, Proteus mirabilis, S. aureus, S. aureus NCIM2079, Shigella flexneri, Lactobacilus casei var shirota by agar well diffusion method. All organisms were sensitive to the extract with inhibitory concentration ranging from 25mg/mL-100mg/mL except Lactobacilus casei var shirota which was resistant to even 100mg/mL concentration of PPE. Flavonoid content of the extract was found to be 10mg quercetin equivalent/g of extract. Full article

Gene knockouts of prcK, prcR and both together were constructed in L. paracasei HD1.7. The antimicrobial activities of the prcK, prcR and prcKprcR mutant strains against B. subtilis were 23.6%, 21.9% and 36.6% lower than that of the parental strain, respectively, indicating that these genes affect production of bacteriocin antimicrobial peptides. qRT-PCR assays showed that the relative transcription levels of prcK and prcR mRNA in the ΔK and ΔR strains were 0.36 and 0.33 times of that in parental bacteria, respectively. Our data suggest that prcK and prcR are quorum sensing related genes that influence production of the bacteriocin Paracin 1.7. This research provides the basis for exploring the functions of these genes in the production of Paracin 1.7 and more generally for the exploration of the biological preservatives instead of chemical preservatives. Full article

Quinolones are bactericidal agents that interfere with the essential prokaryotic enzyme DNA gyrase. While their mechanism of killing appears to be elucidated, one interesting feature is represented by the fact that, under anaerobic conditions, the growth of bacteria is inhibited but their viability is not affected by the first generation of quinolones such as nalidixic acid. More information about the mode of action of these drugs in anaerobiosis might be gained through the availability of strains subjected to enhanced killing in oxygen-deprived media. It has been assumed that when a population of a AB1157(F’lac) strain is exposed to nalidixic acid, plasmid-free cells could be recovered from culture treated with sub-inhibitory concentrations of the drug (2 mg/L) in aerobiosis, and, at the same drug level, only from the rare spontaneous susceptible mutant(s) in anaerobiosis. Among plasmid free bacteria found, 1 isolate demonstrated the same MIC value to nalidixic acid in both aerobic and anaerobic conditions. The mutation was co-transferred with Tn10 inserted at 28.5 min of the Escherichia coli genetic map into a wildtype strain. These transductants revealed the same phenotypes of the original mutant: susceptibility to nalidixic acid under anaerobic conditions (assessed by time-kill tests) and elongated cells during the aerobic growth, generation time about 65 min in comparison to 25 min of the control. Time kill experiment under aerobic environment revealed that the transductant was also susceptible to ciprofloxacin but not nalidixic acid in the presence of chloramphenicol (50 mg/L). These results suggest a possible role of bacterial topoisomerase in the anaerobic susceptibility to nalidixic acid of the mutant. Full article

Lipid fraction from four different culinary condiments namely black seed (Nigella sativa), fennel seeds (Foeniculum vulgare), bay leaf (Laurus nobilis) and coriander seeds (Coriandrum sativum) were investigated for total phenolic content, antioxidant activity, total flavonoid content, total flavonol content and antibacterial attributes. Antimicrobial properties were determined against food-borne bacteria through agar well diffusion, drop agar diffusion, macrobroth dilution with simultaneous determination of their minimum inhibitory concentrations and changes in cellular morphology was analyzed through Scanning electron microscopy. Generally, ethanolic lipid fractions were more effective bioactively as compared to methanolic LFs. Parallel results were obtained for antibacterial activities with the highest antibacterial activities exhibited by ethanolic LFs. The results positively support the use of these lipid fractions in generating new systems to inhibit bacterial growth, extend the shelf life and enhance the safety of the packaged food product. The examined oils can also be used for therapeutic purposes. Full article

This study was conducted to examine the comparative effect on wheat plant health inoculated with the two different rhizobacterial strains Bacillus sp. (JG3) and Pseudomonas sp. (JG7) under soil salinity. Total seven potential salt tolerant strains were isolated from the saline soils of BBAU-Lucknow. The bacterial strains have been investigated for nitrogen fixation, phosphate solubilization, ammonia, indole acetic acid and hydrogen cyanide production activities. Based on morphological and biochemical activities the strains JG3 was designated as Bacillus sp. and the strain JG7 was designated as Pseudomonas sp. Both the strains witness positive for the different plant growth promoting traits. In comparison of strain JG7, strain JG3 inoculated wheat seeds enhance plant height by 32.32%, root length by 37.84%, fresh weight by 28.2% and dry weight by 15.51% in FYM amended soils. We observe in this study that seeds treated with Bacillus sp. found significantly effective in plant growth promotion compared to Pseudomonas sp. in saline soil. Based on the comparative experimental study reported herein, it is pointedly observed that the use of salt tolerant PGPRs are effective for facilitating plant health in salt stress environments. Full article

Lactic Acid Bacteria (LAB) have a great potential as bio-preservatives. The live cells and supernatant Lactococcus lactis subsp. lactis induced bacteriological changes in Onchorhynchus mykiss fillet by spray and immersion methods was studied during vacuum- packaged storage at 4 °C for 15 days. 40 kg of O. mykiss were prepared from a culture farm in Oshnavieh (Northwest Iran) and 112 fillet samples (100g) were prepared by aseptic method. L. lactis subsp. lactis (PTCC1336) bacteria was cultured in MRS culture medium. Its supernatant (2%, 4%) was extracted and 10⁶ CFUml^-1 dilutions of LAB were prepared and tested on the fillets to enhance their shelf life. All samples were evaluated regarding to growth of psychrotrophic, psychrophilic, mesophilic bacteria, molds and yeasts. Four characteristics including of odor, flavor, texture and color of fillets after and before cooking were evaluated for sensory analysis on days 1, 5, 10 and 15 and compared with control samples. The 4% supernatant and live bacteria were more effective than that of 2% and control (P<0.05). The amounts of corrosive bacteria in 4% and live cells in storage time were less than human consumption limits (7log CFUg^-1), whereas in control and 2% supernatant treatments were more than that limits. The results showed that increasing the percentage of supernatant was more effective on bacteriologic factors and enhanced sensory characteristics of rainbow trout fillets (P<0.05). Full article

Water scarcity has resulted to urban residence to resort to using untreated wastewater to irrigate their crops. This practice raises concerns on health of the farmers and consumers of the crops. The study aimed at determining whether the effluent from Boundary Sewage Treatment Plant was up to national and international standards recommended for irrigation, if not they were further subjected to slow sand filtration of different sand sizes (0.1 and 0.05 mm) to polish the effluent. Pour plate method was used to determine total coliforms (TC), Biological oxygen demand (BOD) technique for BOD, chemical oxygen demand (COD) digestion for COD, gravimetric method for total dissolved solids (TDS) and total suspended solids (TSS). One sample t-test during dry season showed that BOD, COD, TC and TSS in the effluent were significantly higher (P<0.05) than the standards for irrigation. During wet season BOD, COD, TDS and pH were significantly not higher (P>0.05) than the compared standards for the wastewater to be used for crop irrigation. The filters improved the effluent from the treatment plant to the standards for irrigation. The sequential treatment of the raw wastewater by the Boundary Sewage Treatment Plant and the slow sand filtration technique made the wastewater to achieve the standards it can be utilized for crop irrigation. Full article