Tolerant Isolates Research Articles

ISOLATION AND DIAGNOSIS OF CADMIUM-RESISTANT BACTERIA AND ITS POTENTIAL PHYTOREMEDIATION WITH THE BROAD BEAN PLANT

Results of the study proved that phytoremediation can be a promising technique to treat cadmium (Cd)-contaminated soil. Four bacteria types were isolated from the soil; two are autotrophic and others are heterotrophic. Autotrophic bacteria were dominant in soils with 42 mg Cd Kg-1. The total count and diversity of both bacteria types decreased with the increase of Cd in media and reached their minimum limit of tolerance at 60 mg Cd L-1 in terms of the heterotrophic bacteria, while the minimum limit of tolerance in the case of autotrophic bacteria was at 110 mg Cd L-1. The four isolates can form biofilms that ranged in thickness between 2.8–4.3 mm. The tolerant isolates belong to Rhizobium leguminosarum, Pseudomonas fluorescens, Actinobacteria, and Corynebacterium. Shoot and dry weight significantly varied according to the changes in Cd concentrations and isolate types. The level in either shoot or root exceeded critical levels, however, its concentration was higher in the root compared with the shoot. The effect of Cd on broad bean plants began at 80 and 100 mg Cd L-1. The broad bean plant was resistant to growing in the contaminated area by Cd even at 120 mg Cd Kg-1 DW. The presence of heterotrophic bacteria was noticeably useful for autotrophic bacteria, as well as, for enhancing Cd resistance. The study showed that cooperative phytoremediation could be a safe and active technique to apply in the field soil contaminated with heavy metals.

Screening of heavy metal stress tolerant fungal isolates for bioremediation and restoration of soil health

Screening of heavy metal stress tolerant fungal isolates for bioremediation and restoration of soil health

Pseudomonas response regulators produced in an E. coli heterologous expression host exhibit host-derived post-translational phosphorylation

In this report, we systematically characterize 32 response regulators (RRs) from a metal tolerant groundwater isolate, Pseudomonas stutzeri RCH2 to assess the impact of host-derived post-translational phosphorylation. As observed by distinct shifted bands in a phos-tag gel, 12 of the 24 detected RRs show homogenous mixtures of phosphorylated proteins or heterogenous mixtures of unphosphorylated and phosphorylated proteins. By evaluating the phosphorylation state of CzcR and CopR II under varying assay parameters, we found that changes to pH and exogenous addition of phospho-donors (e.g. acetyl phosphate) have little to no effect on phosphorylation state. By applying protein production conditions that decrease the pool of intracellular acetyl-phosphate in E. coli, we found a reduction in the phosphorylated population of CopR II when magnesium was added to the medium, but observed no change in phosphorylated population when CopR II is expressed in E. coli BL21 (DE3) ∆pta, a mutant with a metabolic disruption to the acetyl-phosphate pathway. Therefore, the specific mechanism of post-translational phosphorylation of RRs in E. coli remains obscure. These findings show the importance of characterizing the phosphorylation state of proteins when heterologously expressed, since their biochemical and physiological properties can be dependent on post-translational modification.

Identification and Characterisation of the Salt Tolerant Phosphate-Solubilising Bacterial Isolates for Enhancing Soil Fertility

In this study, 13 bacteria were isolated from the agricultural soils of Kyaukse city, Myanmar, and out of these isolates, two bacteria isolates viz. JU-24 and JU-33 are found to be potent phosphate (P) solubilisers and are selected for further studies. These two isolates are identified as Bacillus megaterium based on the 16S rRNA gene sequence. When the growth rates of these two isolates were tested for salt tolerance, they could grow well in media with NaCl concentrations of 3%, 6% and 9%. For 0% and 3% NaCl concentrations, JU-33 (84.37 mg/L for 0% NaCl and 130.36 mg/L for 3% NaCl) showed higher P-solubilising efficiency than JU-24 (73.29 mg/L for 0% NaCl and 87.42 mg/L for 3% NaCl) for both NaCl concentrations when inoculated in Ca3(PO4)2 containing liquid medium. In media containing AlPO4 and FePO4 without NaCl, the P-solubilising activity of JU-24 is higher than JU-33 for these two substrates. Moreover, these strains showed noticeable levels of P solubilisation activity in the presence of various carbon sources indicating high P-solubilising efficacy. The soil inoculation experiment revealed that inoculating the experimental soil with JU-33 resulted in an obvious increase in available P, which increased from 13.08 mg/L in the non-inoculated soil to 18.40 mg/L in the inoculated soil with the bacterial isolate, JU-33. This study clearly showed that JU-24 and JU-33 isolates could be used as biofertilizers in ecological agricultural systems and may help to sustain environmental health and soil productivity. The use of biofertilizers can reduce the use of expensive chemical fertilisers, reducing planting costs and improving soil fertility through long-term use. Biofertilizers can help solve the problem of feeding an increasing global population at a time when agriculture is facing various environmental stresses and are affordable for low-income farmers.

Transcriptome Analysis and SNP Identification Reveal That Heterologous Overexpression of Two Uncharacterized Genes Enhances the Tolerance of Magnaporthe oryzae to Manganese Toxicity.

ABSTRACTManganese is a crucial trace element that constitutes the cofactors of many enzymes. However, excessive Mn2+ can be toxic for both prokaryotes and eukaryotes. The mechanism of fungal genetics and metabolism in response to Mn2+ stress remains understudied, warranting further studies. Magnaporthe oryzae is well-established as the most destructive pathogen of rice. A field strain, YN2046, more sensitive to Mn2+ toxicity than other strains, was obtained from a previous study. Herein, we explored the genetic mechanisms of Mn2+ sensitivity in YN2046 through comparative transcriptomic analyses. We found that many genes previously reported to participate in Mn2+ stress were not regulated in YN2046. These non-responsive genes might cause Mn2+ sensitivity in YN2046. Weight gene correlation network analysis (WGCNA) was performed to characterize the expression profile in YN2046. Some overexpressed genes were only found in the Mn2+ tolerant isolate YN125. Among these, many single nucleotide polymorphism (SNP) were identified between YN125 and YN2046, which might disrupt the expression levels of Mn responsive genes. We cloned two uncharacterized genes, MGG_13347 and MGG_16609, from YN125 and transformed them to YN2046 with a strong promoter. Our results showed that the heterologous overexpression of two genes in YN2046 restored its sensitivity. Transcriptomic and biochemical analyses were performed to understand Mn tolerance mechanisms mediated by the two heterologous overexpressed genes. Our results showed that heterologous overexpression of these two genes activated downstream gene expression and metabolite production to restore M. oryzae sensitivity to Mn, implying that SNPs in responsive genes account for different phenotypes of the two strains under Mn stress.IMPORTANCE Heavy metals are used for fungicides as they target phytopathogen in multiple ways. Magnaporthe oryzae is the most destructive rice pathogen and is threatening global rice production. In the eukaryotes, the regulation mechanisms of Mn homeostasis often focus on the posttranslation, there were a few results about regulation at transcript level. The comparative transcriptome analysis showed that fewer genes were regulated in the Mn-sensitive strain. WGCNA and SNP analyses found that mutations in promoter and coding sequence regions might disrupt the expression of genes involved in Mn detoxification in the sensitive strain. We transferred two unannotated genes that were cloned from the Mn-tolerant strain into a sensitive strain with strong promoters, and the transformants exhibited an enhanced tolerance to Mn2+ toxicity. Transcriptome and biochemistry results indicated that heterologous overexpression of the two genes enhanced the tolerance to Mn toxicity by reactivation of downstream genes in M. oryzae.

Efficacy of weak acid preservatives on spoilage fungi of bakery products

Organic acids and their salts are usually the first choice in the bread industry to restrict fungal spoilage, but their efficacy is pH-dependent and spoilage by fungi remains as a common threat. Therefore, this study aimed to evaluate the susceptibility of spoilage fungi of bakery products to acetic, sorbic, and propionic acids at different pH. Penicillium roqueforti, Penicilium paneum, Aspergillus pseudoglaucus, Aspergillus montevidensis and Hyphopichia burtonii strains isolated from spoiled products had their minimum inhibitory concentration (MIC) defined by macrodilution. The concentrations tested were: (i) sorbic acid up to 32 mM; (ii) propionic acid up to 1024 mM and (iii) acetic acid up to 800 mM with pH adjusted in 4.5, 5.0, 5.0 and 6.0 after setting the agent concentration. The lowest MICs for all agents were obtained at pH 4.5, usually doubling with every 0.5 pH increase. P. roqueforti strains isolated from spoiled products were the most resistant to all tested preservatives; while strains of the related species P. paneum, showed similar tolerance to acetic and propionic acids but was double more susceptible to sorbic acid. Strains of A. pseudoglaucus and A. montevidensis were indistinctly susceptible to the preservatives and were the most susceptible species to propionic and acetic acids. H. burtonii strains demonstrated the most variable behaviour in comparison to the other strains being the most susceptible to sorbic acid, were like Aspergillus strains regarding propionic acid, but tolerate well acetic acid. Propionic acid concentrations usually allowed in baked goods are lower than the concentrations required to inhibit the most tolerant isolates tested in this study. The same is true for sorbic acid at higher pH levels. Spoilage species of bakery ware presents a distinct susceptibility profile to the preservatives commonly used in this sector, but the high tolerance observed is a cause of concern.

Antibiotic spectrum of characterized Lactic Acid Bacteria obtained fromdomestic Dahi samples

From forty lactic acid bacterial isolates obtained from fifteen domestic dahi samples of dahi, thirteen were found to possess probiotic characteristics such as acid and bile tolerance . These acid and bile tolerant lactobacilli isolates further, were identified phenotypically and genotypically as Lb.rhamnosus (5 Nos). Lb. fermentum (3 Nos), Lb. plantarum (3 Nos) and Lb. delbrueckii ssp. bulgaricus (2 Nos). The identified cultures were subjected for the antibiotic test using the disc diffusion technique against Penicillin (10µg), Gentamycin (10µg), Streptomycin (10µg), Chloramphinicol (10µg), Kanamycin (30µg) Erythtomycin (15µg) and Bacitracin (10 µg). All the five strains of Lb.rhamnosus strains were susceptible to all the seven antibiotics tested as they showed more than 10 mm diameter inhibitory zone. Similarly all the three strains of Lb.plantarum, Lb.fermentum and Lb.delbruckii ssp. bulgaricus were susceptible to all the antibiotics to varying degrees. In this study the results clearly demonstrate the susceptible nature of the probiotic Lactobacilli isolates against the commonly used antibiotics.

Fungal-bacterial biofilm mediated heavy metal rhizo-remediation.

Heavy metal pollution due to excessive use of chemical fertilizers (CF) causes major damage to the environment. Microbial biofilms, closely associated with the rhizosphere can remediate heavy metal-contaminated soil by reducing plant toxicity. Thus, this study was undertaken to examine the remedial effects of microbial biofilms against contaminated heavy metals. Fungi and bacteria isolated from soil were screened for their tolerance against Cd2+, Pb2+, and Zn2+. Three bacterial and two fungal isolates were selected upon the tolerance index (TI) percentage. Fungal-bacterial biofilms (FBBs) were developed with the most tolerant isolates and were further screened for their bioremediation capabilities against heavy metals. The best biofilm was evaluated for its rhizoremediation capability with different CF combinations using a pot experiment conducted under greenhouse conditions with potatoes. Significantly (P < 0.05), the highest metal removal percentage was observed in Trichoderma harzianum and Bacillus subtilis biofilm under in situ conditions. When compared to the 100% recommended CF, the biofilm with 50% of the recommended CF (50CB) significantly (P < 0.05) reduced soil available Pb2+ by 77%, Cd2+ by 78% and Zn2+ by 62%. In comparison to initial soil, it was 73%, 76%, and 57% lower of Pb2+, Cd2+, and Zn2+, respectively. In addition, 50CB treatment significantly (P < 0.05) reduced the metal penetration into the tuber tissues in comparison with 100C. Thus, the function of the developed FBB with T. harzianum-B. subtilis can be used as a potential solution to remediate soil polluted with Pb2+ Cd2+ and Zn2+ metal contaminants.

Clemastine Inhibits the Biofilm and Hemolytic of Staphylococcus aureus through the GdpP Protein.

ABSTRACTStaphylococcus aureus poses a significant threat to human health due to its virulence and multidrug resistance. In addition, recalcitrant biofilm formation of S. aureus often results in chronic infection and the treatment tolerance toward the traditional antibiotics. Thus, the development of novel antimicrobial agents capable to inhibit or eradicate S. aureus biofilm formation does matter. Here, we demonstrated that clemastine showed slight bacteriostatic activity and enhanced the antibacterial activity of oxacillin against S. aureus. Moreover, the dramatic inhibition of biofilm formation was found in clinical S. aureus strains by clemastine. Clemastine inhibited the release of eDNA during the biofilm formation and decreased the S. aureus hemolytic activity. Moreover, the S. aureus SA113 treated with clemastine displayed the decreased transcriptional level of the biofilm formation relevant genes (fnbB, icaA, and icaB), virulence genes (hlg, hld, lukde, lukpvl, beta-PSM, delta-PSM, and cap5A), and the regulatory genes agrA. The proteomics analysis of SA113 treated with clemastine demonstrated the significant changes in levels of biofilm-related proteins (stress response regulators ClpB and GroS, ATP-binding proteins, and urease metabolism), virulence-related proteins (SspA, superantigen, and VWbp), and methicillin resistance-related proteins (glutamine metabolism). The genetic mutations on gdpP (cyclic di-AMP phosphodiesterase) were found in the clemastine-induced tolerant derivative isolate by whole-genome sequencing. Furthermore, the interaction between clemastine and GdpP protein was demonstrated by the molecular docking, gdpP overexpression experiment, and thermal stability assay. Conclusively, clemastine might exert its inhibitory effects against the biofilm formation and hemolysis in S. aureus through targeting GdpP protein.IMPORTANCE The biofilm formation, which protects bacteria from stresses, including antibiotics and host immune responses, can be commonly found in clinical S. aureus isolates worldwide. Treatment failure of traditional antibiotics in biofilm-associated S. aureus infections remains a serious challenge. The novel anti-biofilm drug is urgently needed to address the looming crisis. In this study, clemastine, which is a histamine receptor H1 (HRH1) antagonist, was found to have a novel role of the significant inhibition against the biofilm formation and hemolytic activity of S. aureus and enhanced antibacterial activity against S. aureus when used in combination with oxacillin by targeting the GdpP protein. The discovery of this study identified novel use and mechanism of action of clemastine as a potential anti-biofilm drug for clinical application for S. aureus infectious.

Chlorine Tolerance and Cross-Resistance to Antibiotics in Poultry-Associated Salmonella Isolates in China.

Chlorine disinfectants have been widely used in the poultry supply chain but this exposure can also result in the development of bacterial tolerance to chlorine and this is often linked to antibiotic cross-resistance. The objectives of this study were to investigate sodium hypochlorite (NaClO) tolerance of Salmonella isolated from poultry supply chains and evaluate cross-resistance. We collected 172 Salmonella isolates from poultry farms, slaughter houses and retail markets in China during 2019–2020. We found that S. Enteritidis, S. Kentucky, and S. Typhimurium constituted > 80% of our Salmonella isolates. Overall, 68% of Salmonella isolates were resistant to > 3 antibiotics and S. Kentucky displayed a significantly (p > 0.05) higher frequency (93.2%) of multidrug resistance than the other serovars. Tolerance to chlorine at MIC > 256 mg/L was detected in 93.6% of isolates (161/172) and tolerant isolates displayed higher decimal reduction times (D value) and less ultrastructural damage than did the suspectable strains under chlorine stress. Spearman analysis indicated significant positive correlations between chlorine tolerance (evaluated by the OD method) and antibiotic resistance (p < 0.05) to ceftiofur, tetracycline, ciprofloxacin and florfenicol and this was most likely due to efflux pump over-expression. The most frequently detected chlorine resistance gene was qacEΔ1 (83.1%, n = 143) and we found a positive correlation between its presence and MIC levels (r = 0.66, p < 0.0001). Besides, we found weak correlations between chlorine-tolerance and antibiotic resistance genes. Our study indicated that chlorine disinfectants most likely played an important role in the emergence of chlorine tolerance and spread of antibiotic resistance and therefore does not completely control the risk of food-borne disease. The issue of disinfectant resistance should be examined in more detail at the level of the poultry production chain.

ISOLATION, CHARACTERIZATION AND IDENTIFICATION OF MULTIFACETED HALOTOLERANT BACILLUS LICHENIFORMIS AND BACILLUS WUDALIANCHIENSIS FROM RHIZOSPHERIC SOILS OF BANGALORE

Plant growth promotion through versatile microorganisms inhabiting the rhizospheric region of the soil has emerged as a sustainable approach in improving the crop productivity and crop health management. The present study reports the isolation and characterization of halotolerant as well as drought tolerant isolates that possess exceptional plant growth promotional attributes. Out of 32 isolates obtained, 13 isolates exhibited excellent plant growth promotional attributes such as phosphate solubilization, phytohormone production, siderophore production etc. Among 13 isolates tested for stress tolerance studies, two isolates Mulberry -1 and Ragi-7 were able to tolerate both drought and saline stresses and were further identified as Bacillus licheniformis and Bacillus wudalianchiensis based on biochemical and molecular techniques. Antibiosis activity of both the isolates tested against two important plant pathogens Fusarium oxysporum and Phomopsis vexans was found to be positive. Bacillus licheniformis and Bacillus wudalianchiensis were further tested for their efficacy to solubilize five different inorganic phosphate sources. The amount of phosphate liberated was found to be highest (3562 mgml-1 and 1894 mgml-1) with diammonium phosphate followed by single super phosphate and tricalcium phosphate with respect to Bacillus licheniformis and Bacillus wudalianchiensis. Zea mays L. seeds treated with the culture filtrate of both the isolates were cultivated on Murashige-Skoog medium under In-vitro conditions. Bacillus wudalianchiensis was found to be better compared to Bacillus licheniformis with respect to plant growth promotional aspects as they were able to increase the root and shoot length of Zea mays L. under In-vitro conditions. Application of the multifaceted capabilities of unexplored halotolerant strain of Bacillus wudalianchiensis could open up a new avenue in plant biotechnology.

Isolation and characterization of chromium (VI) tolerant bacteria from tannery effluents.

The tannery industry is a potent environment polluting agent worldwide. Chromium (VI) is a major heavy metal in tannery effluents and their accumulation in soil and water is a serious environmental problem. This study investigates the capacity of indigenous bacteria isolated from tannery effluents for tolerance to chromium (VI). The chromium tolerance of isolates assessed through both agar dilution and broth microdilution methods. Isolates were identified by morphological and biochemical analysis. The tolerance of isolates to cadmium, nickel, lead, and vanadium and also their multidrug-resistant (MDR) profile were determined. Then the top isolate was characterized via 16S rRNA sequencing and its growth temperature and pH were optimized. Finally, the kinetic of chromium biosorption and chromium removal efficiency was determined using a Nutrient broth medium and wastewater containing 20mg/L chromium, respectively. Of 32 screened chromium tolerant isolates, 14 isolates with higher chromium tolerance were selected for further study. 78.57% of isolates represented simultaneous MDR and Multi Heavy Metal tolerance (MHMT) phenotypes and MDR indices of 0.2-1 indicating their source from niches with high antibiotic contamination. However, there was no significant correlation between MDR and MHMT phenotypes among isolates. The top isolate was identified as Lactococcus lactis and showed optimal growth at pH6 and 25°C. The maximum chromium biosorption occurred at the end of the exponential phase upon optimized conditions and the approximate chromium removal efficiency of 52.5% was obtained. The isolated bacteria specifically L. lactis after more evaluations, may show the potential for bioremediation of chromium from tannery effluents.

Bioreduction potential of chromate resistant bacteria isolated from chromite mine water of Sukinda, Odisha

Chromite mine water with a high concentration of Cr(VI) harbors highly chromium resistant bacteria, which could benefit the mine environment and be used for economic bioremediation strategy for chromate polluted ecosystems. In the present investigation, eight comparatively high chromium tolerant (≥500 mg L−1) bacteria were isolated from water samples of the Sukinda chromite mine environment. Their morpho-biochemical and molecular (16S rRNA gene sequencing) characterization revealed that most of the bacteria belong to the members of the genus Bacillus, Lysinibacillus boronitolerens, and Alcaligenes faecalis. It was observed that all the eight bacterial isolates could reduce above 90% of Cr(VI) (p < 0.05) within 288 h. Out of these eight isolates, Alcaligenes faecalis (CWB-4) could able to reduce the maximum (99.77%) supplied Cr(VI) after 144 h, as the most efficient Cr (VI) reducing strain whereas, Licinibacillus boronitolerens (CWB-2) showed the least Cr(VI) reduction ability. The enzyme activities of the eight isolates were in the range of 0.67 to 5.07 U mL−1. Hence, the high chromate tolerant bacterial isolates, with Cr (VI) reducing potential isolated in the present study, could be considered promising biological agents for bioremediation of environments polluted with chromium.

Isolation, characterization and degradation performance of oxytetracycline degrading bacterium Planococcus sp. strain pw2.

Oxytetracycline (OTC), is a widely used veterinary antibiotic for treatment and prophylaxis in aquaculture. As an emerging pollutant, OTC in the environment exerts selective pressure on aquatic organisms causing proliferation of antibiotic resistant genes. In the present study, an OTC tolerant isolate labelled as pw2 was selected among the 11 OTC tolerant isolates, isolated from the aquaculture effluent, for investigating its OTC degrading potential. The cell morphology, biochemical characteristics, and 16S ribosomal RNA (rRNA) gene sequence of the isolated strain indicated that it belonged to the genus Planococcus. The OTC removal percentage was estimated through measuring its residual concentration in the culture medium with high performance liquid chromatography. The strain exhibited maximum removal efficiency of 90.62%, with initial OTC concentration of 10µg/ml. The optimum degrading conditions were 35°C and pH 7. The degradation rate of OTC with (biotic) and without strain pw2 (abiotic) was 3.253 and 1.149mg/l/d, respectively. The half-life was recorded to be 2.13 d in the presence of strain pw2, in contrast to 6.03days recorded without strain pw2. The total (biotic + abiotic) OTC degradation efficiency was 75.74, 83.93, 90.62, and 86.47% for the initial OTC concentrations of 1 to 25µg/ml, respectively. Addition of carbon and nitrogen did not influence the OTC removal which indicates Planococcus sp. pw2 use OTC as sole energy source. Thus, Planococcus sp. pw2 plays a vital role in reducing the OTC concentration in the environment, offering a promising method for treatment of aquaculture effluent containing OTC.

Screening and characterization of potential cyanide tolerating lactic acid bacteria from cassava pulp juice

Lactic acid bacteria are predominant microorganisms that play important roles during cassava fermentation. Most efforts to develop cyanide tolerant isolates for cassava fermented products have been unsuccessful because of cyanide toxicity in cassava tubers. The objectives of this study were identifying cyanide tolerating bacteria and study their tolerability efficiency. 119 lactic acid bacteria were isolated from fermented cassava pulp juice. Out of the total isolated bacteria, ten potential cyanide tolerating bacteria was screened. The cyanide tolerance efficiency was studied at 100, 400, 600 and 8000mg/L potassium cyanide, growth at different temperature and pH were analyzed. The maximum growth rate reading of the screened isolates ranges (0.674 to 1.116) at 600nm in maximum cyanide concentration. Isolate CD1, LA2, LA1 and CD2 showed maximum cyanide tolerance of (74.4, 72.66, 70.66 and 68.73%) respectively at 800mg/l after 48hr of incubation. The cyanide tolerability potential of individual isolates varies across different cyanide concentration. Above all 10 isolates were resistant to maximum cyanide concentration and possess potential of cyanide tolerating properties that help their selection and application in a controlled process to detoxify cassava roots for food and feed utilization. There was a general decrement in all samples over 48 h fermentation periods from 6.00 to 3.18 and the bacterial isolates showed significant growth at room temperature which were between ʺ25°Cʺ and ʺ40°Cʺ.

Proteomics of Two Thermotolerant Isolates of Trichoderma under High-Temperature Stress.

Several species of the soil borne fungus of the genus Trichoderma are known to be versatile, opportunistic plant symbionts and are the most successful biocontrol agents used in today’s agriculture. To be successful in field conditions, the fungus must endure varying climatic conditions. Studies have indicated that a high atmospheric temperature coupled with low humidity is a major factor in the inconsistent performance of Trichoderma under field conditions. Understanding the molecular modulations associated with Trichoderma that persist and deliver under abiotic stress conditions will aid in exploiting the value of these organisms for such uses. In this study, a comparative proteomic analysis, using two-dimensional gel electrophoresis (2DE) and matrix-assisted laser desorption/time-of-flight (MALDI-TOF-TOF) mass spectrometry, was used to identify proteins associated with thermotolerance in two thermotolerant isolates of Trichoderma: T. longibrachiatum 673, TaDOR673 and T. asperellum 7316, TaDOR7316; with 32 differentially expressed proteins being identified. Sequence homology and conserved domains were used to identify these proteins and to assign a probable function to them. The thermotolerant isolate, TaDOR673, seemed to employ the stress signaling MAPK pathways and heat shock response pathways to combat the stress condition, whereas the moderately tolerant isolate, TaDOR7316, seemed to adapt to high-temperature conditions by reducing the accumulation of misfolded proteins through an unfolded protein response pathway and autophagy. In addition, there were unique, as well as common, proteins that were differentially expressed in the two isolates studied.

The Effect of Triclosan Adaptation on Antimicrobial Resistance among Clinical Escherichia coli Isolates from Egyptian Patients

There is a possible link between exposure to Triclosan (TCS) and changes in antimicrobial susceptibility. The change in the tolerance of clinical Escherichia coli (n=45) isolates to the biocide TCS, changes in antibiotic resistance and differences in the efflux pump mechanism were analyzed. 45 E. coli isolates were obtained. The minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) of TCS, and the expression of four efflux pump encoding genes in antibiotic-resistant isolates were determined before and after TCS adaptation. The number of TCS-tolerant isolates was 11 (24.4%). After adaptation, the percentage of tolerant isolates increased to 42.2% (n=19). A significant change (p&lt;0.05) in antimicrobial resistance of the tested isolates (n=45) before and after TCS adaptation was detected for ceftazidime, ceftriaxone, ertapenem, imipenem, amikacin, gentamicin, tobramycin, ciprofloxacin, levofloxacin and doxycycline. Among the new TCS tolerant isolates (n=8). there was an increase in TCS MIC as well as the MBC after TSC adaptation. The adapted isolates exhibited a significant increase in the expression of mdfA and norE genes (p=&lt;0.001). There is a strong correlation between efflux pump gene overexpression and susceptibility to TCS and other antimicrobials.

Assessing Antibiotic Tolerance of Staphylococcus aureus Derived Directly from Patients by the Replica Plating Tolerance Isolation System (REPTIS).

Antibiotic-tolerant Staphylococcus aureus poses a great challenge to clinicians as well as to microbiological laboratories and is one reason for treatment failure. Antibiotic-tolerant strains survive transient antibiotic exposure despite being fully susceptible in vitro. Thus, fast and reliable methods to detect tolerance in the routine microbiology laboratory are urgently required. We therefore evaluated the feasibility of the replica plating tolerance isolation system (REPTIS) to detect antibiotic tolerance in Staphylococcus aureus isolates derived directly from patients suffering from different types of infections and investigated possible connections to clinical presentations and patient characteristics. One hundred twenty-five S. aureus isolates were included. Replica plating of the original resistance testing plate was used to assess regrowth in the zones of inhibition, indicating antibiotic tolerance. Bacterial regrowth was assessed after 24 and 48 h of incubation, and an overall regrowth score (ORS) was assigned. Regrowth scores were compared to the clinical presentation. Bacterial regrowth was high for most antibiotics targeting protein synthesis and relatively low for antibiotics targeting other cellular functions such as DNA replication, transcription, and cell wall synthesis, with the exception of rifampin. Isolates with a blaZ penicillinase had lower regrowth in penicillin and ampicillin. Low ORSs were more prevalent among isolates recovered from patients with immunosuppression or methicillin-resistant S. aureus (MRSA) isolates. In conclusion, REPTIS is useful to detect antibiotic tolerance in clinical microbiological routine diagnostics. Further studies should evaluate the impact of rapid detection of antibiotic tolerance as a clinical decision-making tool for tailored antibiotic treatments.

English

Salinity stress is one of the critical factors that limits agricultural productivity particularly in the arid to semi-arid regions worldwide. Elevated concentrations of soluble salts especially NaCl cause osmotic stress, ionic stress and imbalance in the uptake of essential nutrients. Use of salt tolerant rhizobacterial isolates have gained much attention now-a-days on account of their environment friendly nature and effectiveness. Therefore, current study was executed to isolate salt tolerant bacteria from the rhizosphere of maize and check their salt tolerance and plant growth promotion under salinity stress. Selected isolates were further investigated in a growth room trial to compare their efficiency in improving growth and physiology of maize. Salinity stress caused a significant reduction in all the measured traits however, inoculation of rhizobacteria modulated its effects and improved maize growth. Among different strains, SUA-14 caused maximum increment in the shoot length (41%), root length (96%), shoot fresh (1.8 fold) and dry weight (1.3 fold), root fresh (1.76 fold) and dry weight (2 fold), salt tolerance index (1.6 fold), chl ‘a’ contents (2.6 fold) and chl ‘b’ contents (2.3 fold) as compared to its respective uninoculated control. Whereas, rhizobacterial strain SHM-5, SHM-13 and SUA-14 showed statistically nonsignificant response in terms of increasing carotenoid contents by 1.8 fold in comparison with their corresponding control. Pearson correlation coefficient showed a strong positive correlation between growth and physiological attributes under salinity stress. On the basis of PCA, SUA-14 found to be the most efficient strain followed by SHM-13. Using 16 S rRNA sequencing, SUA-14 and SHM-13 were identified as Acinetobacter and Bacillus species respectively.

EXPLORING THE ABIOTIC AND BIOTIC STRESS TOLERANCE POTENTIAL OF RHIZOBACTERA ISOLATED FROM CYAMOPSIS

Agriculture plays a vital role for any economy primarily for developing and under developed economies. Increasing abiotic as well as biotic stresses adversely affects crop productivity across the world. Microorganisms inhabiting the Rhizospheric region of plant soil are known to play an important role in alleviating these stresses, thus enhancing crop productivity and yield. The present study was carried out to isolate the Rhizospheric bacteria from Cyamopsis showing potential to tolerate abiotic and biotic stresses. To carry out this, bacteria were isolated from Rhizospheric soil of Cyamopsis which were collected from different regions of Gujarat. These isolates were screened for tolerance to different abiotic stresses such as temperature, pH, salt and drought. Highly abiotic stress tolerant isolates were further tested for biotic stress against pathogenic bacteria and fungi. Among the 80 bacterial isolates, best grown 30 cultures were tested for different abiotic stress. Four cultures i.e. MN40, KM1, KM6 and AK17 showing high tolerance to abiotic stresses were further investigated for biotic stress tolerance. Selected cultures were tested for their antagonistic activity against pathogenic fungi viz., Macrophomina phaseolina, Fusarium oxysporium, Sclerotinum rolfissii and Trichoderma spp. Furthermore, antimicrobial activities of all 4 selected bacterial strains were tested against different test organisms viz., Gram negative bacteria (Salmonella typhi) and Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus). Amongst the 4 selected bacterial strains, KM6 shows highest antagonistic activity.