Inhibitory activities of Typhonium trilobatum (L.) Schott on virulence potential of multi-drug resistant toxigenic Vibrio cholerae.

Cholera is a serious epidemic disease caused by the toxigenic strains of Vibrio cholerae belonged to O1 or O139 serogroups. The emergence of antibacterial resistance in V. cholerae is an increasing concern. Natural product drug invention and Ethnopharmacology may demonstrate a considerable expectation under this circumstance. Traditionally, leaves of Typhonium trilobatum (L.) Schott (locally known as Ghatkanchu or Bengal Arum) are employed for treatment of gastrointestinal disorder in different region of India. The objective of the present study was to evaluate the antibacterial, and antibiofilm activities of methanol extract of T. trilobatum leaves (METTL) against the strains of multi-drug resistant (MDR) Vibrio cholerae (serotypes O1, O139, non-O1, and non-O139) which are responsible for watery diarrhea such as cholera. MIC, MBC and time-kill kinetic studies were used for evaluation of In vitro antibacterial activity of METTL. Microdilution method and Confocal laser scanning microscopy were used to evaluate biofilm-inhibitory activities. The gene expression was analyzed by performing Quantitative real-time PCR (qRT-PCR). METTL showed antibacterial activity with MIC and MBC at 1-32 mg/mL and 8-32 mg/mL, respectively against the clinical strains of Vibrio cholerae belonged to different serogroups. METTL showed significant (P < 0.05) inhibitory activity on the formation of biofilm by V. cholerae SG24, with 81.3, 75.8, and 69.6% of inhibition at MIC, ½ MIC and » MIC, respectively. METTL showed also significant (P < 0.05) inhibitory activity on the formation of extracellular polymeric substances (EPS) formation by V. cholerae SG24, with 89.41, and 99.26% of inhibition of EPS protein and EPS carbohydrate at MIC, respectively. METTL significantly (p < 0.01) inhibited the Cholera toxin (CT) production by the V. cholerae strain SG24 evaluated by the CT - ELISA assay. The cholera toxin production was reduced by 76.26%, 48.76% and 29.93 at MIC (8 mg/mL), ½ MIC (4 mg/mL) and » MIC (2 mg/mL), respectively. METTL was shown to repress ctxAB gene transcription 1.76 fold (p < 0.05) at sub-bactericidal concentration (» MIC). We also found that the expression of cholera toxin activator genes, toxT and tcpP was reduced by 11.56- fold (p < 0.001) and 23.52- fold (p < 0.001), respectively, at sub-bactericidal concentration (» MIC). Transcription of the following genes was repressed: vpsR (1.8-fold; p < 0.05), Bap1 (1.53-fold; p ≤ 0.05), and rmbA (2.89-fold) by METTL at sub-bactericidal concentration. The expression of vpsT was also repressed by 1.5-fold (p < 0.01) at sub-bactericidal concentration. The active Typhonium trilobatum (L.) leaves extract may be suggested as an substitute for the treatment of MDR V. cholerae infection and could be used as prospective source for the development of novel antimicrobial compound/s and biofilm-inhibitory drug/s useful for the treatment of cholera and diarrheal patients. The results obtained here also validate scientifically the traditional uses of Typhonium trilobatum (L.) in India employed for the treatment of gastrointestinal disorder. Further studies should be directed at purifying and characterizing these antibacterial principles against Vibrio cholerae.

Antibacterial substances produced by pathogen inhibitory gut bacteria in Labeo rohita: Physico-chemical characterization, purification and identification through MALDI-TOF mass spectrometry.

Application of antibiotics to combat bacterial diseases in fish has been criticized due to likely emergence of drug resistance. Therefore, investigation of new bioactive compounds from natural sources has been taken into account. This study was designed to purify and characterize the bioactive compound in the cell free supernatant (CFSs) of autochthonous gut bacteria (Bacillus methylotrophicus KU556164, B. amyloliquefaciens KU556165, Pseudomonas fluorescens KU556166 and B. licheniformis KU556167) isolated from rohu, Labeo rohita. CFSs were antagonistic to fish pathogenic Aeromonas spp., moderately thermo-tolerant and active in wide range of pH (5-11). Antibacterial activity of the CFSs was reduced by the action of proteases (e.g., Proteinase K and Trypsin), indicating proteinaceous nature of the bioactive compound like the bacteriocins. Three-step purification procedure resulted in recovery of 16.97%, 18.04%, 33.33% and 6.38% activity of the antimicrobial protein produced by B. methylotrophicus, B. amyloliquefaciens, P. fluorescens and B. licheniformis, respectively. Purification at each step revealed decrease in protein content with gradual increase in the specific activity of the antimicrobial protein. The purified antibacterial compound ranged between 18.2 and 25.6 kDa. Identification through MALDI-TOF MS/MS and database search through Mascot search engine predicted that the bactericidal compound belonged to either alkaline proteases, or, transcriptional regulator and some hypothetical proteins. Apart from potential technological application of the antibacterial compound, the present study might show promise for application of gut-associated bacteriocinogenic bacteria to control diseases in fish caused by pathogenic bacteria.

Vanillin biotechnology: the perspectives and future.

The biotechnological production of fragrances is a recent trend that has expanded rapidly in the last two decades. Vanillin is the second most popular flavoring agent after saffron and is extensively used in various applications, e.g., as a food additive in food and beverages and as a masking agent in various pharmaceutical formulations. It is also considered a valuable product for other applications, such as metal plating and the production of other flavoring agents, herbicides, ripening agents, antifoaming agents, and personal and home-use products (such as in deodorants, air fresheners, and floor-polishing agents). In general, three types of vanillin, namely natural, biotechnological, and chemical/synthetic, are available on the market. However, only natural and nature-identical (biotechnologically produced from ferulic acid only) vanillins are considered as food-grade additives by most food-safety control authorities worldwide. In the present review, we summarize recent trends in fermentation technology for vanillin production and discuss the importance of the choice of raw materials for the economically viable production of vanillin. We also describe the key enzymes used in the biotechnological production of vanillin as well as their underlying genes. Research to advance our understanding of the molecular regulation of different pathways involved in vanillin production from ferulic acid is still ongoing. The enhanced knowledge is expected to offer new opportunities for the application of metabolic engineering to optimize the production of nature-identical vanillin. © 2018 Society of Chemical Industry.

Beneficial effects of bio-controlling agent Bacillus cereus IB311 on the agricultural crop production and its biomass optimization through response surface methodology.

Disease in agricultural field is a big problem that causes a massive loss in production. In this present investigation, we have reported a soil-borne bacterium Bacillus cereus IB311 which is antagonistic to plant pathogens (Pseudomonas syringae and Agrobacterium tumefaciens), and could make a substantial contribution to the prevention of plant diseases. To prove the practical application, the strain was directly applied in agricultural field. The results demonstrated that B. cereus IB311 has increased the production (20% and 26% in term of average pod number per plant, average seed number per pod, and seed yield per experimental plot) in ground nut (Arachis hypogaea var. Koushal, G201) and sesame (Sesamum indicum var. Kanak), respectively. To reduce the production cost, the biomass production was optimized through response surface methodology (RSM). Interactions of three variables (glucose, beef extract and inoculum) were studied using Central Composite Design. According to our analysis, optimum production of Bacillus cereus IB311 (5.383 µg/ mL) may be obtained at glucose 1.985%, beef extract 1.615% and inoculums size 0.757%. Therefore, we strongly believe that the application of this strain in agricultural field as bio-controlling agent will definitely enhance the production yield and will reduce the disease risk.

Assessment of hemolytic activity, enzyme production and bacteriocin characterization of Bacillus subtilis LR1 isolated from the gastrointestinal tract of fish.

In the present investigation, probiotic potential (antagonistic activity, enzyme production, hemolytic activity, biosafety, antibiotic sensitivity and bile tolerance level) of Bacillus subtilis LR1 was evaluated. Bacteriocin produced by the bacterial strain B. subtilis LR1 isolated from the gastrointestinal tract of Labeo rohita was purified and characterized. The molecular weight of the purified bacteriocin was ~50 kDa in 12 % Native PAGE and showed inhibitory activity against four fish pathogens such as Bacillus mycoides, Aeromonas salmonicida, Pseudomonas fluorescens and Aeromonas hydrophila. The purified bacteriocin was maximally active at temperature 40 °C and pH 7.0, while none of the tested surfactants affect the bacteriocin activity. Extracellular enzyme activity of the selected bacterial strain was also evaluated. Amylase activity was estimated to be highest (38.23 ± 1.15 µg of maltose liberated mg-1 protein ml-1 of culture filtrate) followed by cellulase and protease activity. The selected bacterium was sensitive to most of the antibiotics used in this experiment, can tolerate 0.25 % bile salt and non-hemolytic in nature. Finally, the efficiency of the proposed probiotic candidate was evaluated in in vivo condition. It was detected that the bacterial strain can effectively reduce bacterial pathogenicity in Indian major carps.

The talking language in some major Gram-negative bacteria.

Cell-cell interaction or quorum sensing (QS) is a vital biochemical/physiological process in bacteria that is required for various physiological functions, including nutrient uptake, competence development, biofilm formation, sporulation, as well as for toxin secretion. In natural environment, bacteria live in close association with other bacteria and interaction among them is crucial for survival. The QS-regulated gene expression in bacteria is a cell density-dependent process and the initiation process depends on the threshold level of the signaling molecule, N-acyl-homoserine lactone (AHL). The present review summarizes the QS signal and its respective circuit in Gram-negative bacteria. Most of the human pathogens belong to Gram-negative group, and only a few of them cause disease through QS system. Thus, inhibition of pathogenic bacteria is important. Use of antibiotics creates a selective pressure (antibiotics act as natural selection factor to promote one group of bacteria over another group) for emerging multidrug-resistant bacteria and will not be suitable for long-term use. The alternative process of inhibition of QS in bacteria using different natural and synthetic molecules is called quorum quenching. However, in the long run, QS inhibitors or blockers may also develop resistance, but obviously it will solve some sort of problems. In this review, we also have stated the mode of action of quorum-quenching molecule. The understanding of QS network in pathogenic Gram-negative bacteria will help us to solve many health-related problems in future.

Autochthonous Gut Bacteria in Two Indian Air-breathing Fish, Climbing Perch (Anabas testudineus) and Walking Catfish (Clarias batrachus): Mode of Association, Identification and Enzyme Producing Ability.

Scanning electron microscopy (SEM) was used to define the location of epithelium-associated bacteria in the gastrointestinal (GI) tract of two Indian air-breathing fish, the climbing perch (Anabas testudineus) and walking catfish (Clarias batrachus). The SEM examination revealed substantial numbers of rod shaped bacterial cells associated with the microvillus brush borders of enterocytes in proximal (PI) and distal regions (DI) of the GI tract of both the fish species. Ten (two each from the PI and DI of climbing perch and three each from the PI and DI of walking catfish) isolated bacterial strains were evaluated for extracellular protease, amylase and cellulase production quantitatively. All the bacterial strains exhibited high cellulolytic activity compared to amylolytic and proteolytic activites. Only two strains, CBH6 and CBH7, isolated from the DI of walking catfish exhibited high proteolytic activity. Maximum cellulase activity was exhibited by the strain, CBF2, isolated from the PI of climbing perch. Six most promising enzyme-producing adherent bacterial strains were identified by 16S rDNA gene sequence analysis. The strain ATH1 (isolated from climbing perch) showed high similarity fo Bacillus amyloliquefaciens whereas, the remaining five strains (isolated from walking catfish) were most closely related to Bacillus licheniformis.

Probable Role of Type IV Pili of Aeromonas hydrophila in Human Pathogenicity.

BACKGROUND: Aeromonas hydrophila is a widely recognized broad-spectrum pathogen that primarily targets the gastrointestinal tract. Type IV pili (T4P) are proteinaceous nano-machines located on the bacterial cell surface, playing a crucial role in host colonization and infection. Regrettably, the T4P systems of A. hydrophila remain largely underexplored. METHODS: A. hydrophila genomes with complete genome assembly and annotation reports up to 31 March 2023, were obtained from the NCBI Genome database or KEGG genome database, followed by a global search for T4P secretion system genes. Protein sequences of these manually curetted genes were used as secondary quarry for Synteny analysis. Protein-protein interaction analysis was performed by string analysis and in silico study of genomic islands. RESULTS: We identified 27 orthologs of type IV pili (T4P) nano-machine components in A. hydrophila. These orthologs are primarily distributed across three operons: pilABCD, pilMNOPQ, and pilVWXY. While the first two operons are commonly found in all experimental genomes, the presence of the pilVWXY operon, coding for 11 orthologs, is reported here for the first time in A. hydrophila. Notably, the complete pilVWXY operon is absent in nonvirulent strains. A genomic islands study between a nonvirulent and hypervirulent strain also confirms absence of most of the genes coded by pilVWXY in nonvirulent strain. Interestingly, among the 51 experimental genomes analyzed, the pilVWXY operon was completely absent in 10 strains, most of which are categorized as nonvirulent; Conclusions: The distribution of two major type IV pili (T4P) nano-machines, PilABCDMNOPQ and PilVWXY, is reported here for the first time in A. hydrophila. Additionally, this study suggests a potential role for the PilVWXY nano-machine in establishing human disease.

Protocol for the construction and functional profiling of metagenome-assembled genomes for microbiome analyses.

Constructing metagenome-assembled genomes (MAGs) from complex metagenomic samples involves a series of bioinformatics operations, each requiring deep bioinformatics knowledge. Here, we present a protocol for constructing MAGs and conducting functional profiling to address biological questions. We describe steps for system configuration, data downloads, read processing, removal of human DNA contamination, metagenomic assembly, and statistical quality assessment of the final assembly. Additionally, we detail procedures for the construction and refinement of MAGs, as well as the functional profiling of MAGs.

Akkermansia muciniphila - A Potential Next-generation Probiotic for Non-alcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of liver conditions, and its growing prevalence is a serious concern worldwide, especially in Western countries. Researchers have pointed out several genetic mutations associated with NAFLD; however, the imbalance of the gut microbial community also plays a critical role in the progression of NAFLD. Due to the lack of approved medicine, probiotics gain special attention in controlling metabolic disorders like NAFLD. Among these probiotics, Akkermansia muciniphila (a member of natural gut microflora) is considered one of the most efficient and important bacterium in maintaining gut health, energy homeostasis, and lipid metabolism. In this perspective, we discussed the probable molecular mechanism of A. muciniphila in controlling the progression of NAFLD and restoring liver health. The therapeutic potential of A. muciniphila in NAFLD has been tested primarily on animal models, and thus, more randomized human trials should be conducted to prove its efficacy.

Indoor Bacterial and Fungal Burden in "Moldy" versus "Non-Moldy" Homes: A Case Study Employing Advanced Sequencing Techniques in a US Metropolitan Area.

The presence of fungi in the indoor environment is associated with allergies and other respiratory symptoms. The aim of this study was to use sequencing and molecular methods, including next-generation sequencing (NGS) approaches, to explore the bacterial and fungal communities and their abundance in the indoor environment of houses (n = 20) with visible "moldy" (HVM) and nonvisible "non-moldy" (HNM) in Memphis, TN, USA. Dust samples were collected from air vents and ground surfaces, and the total DNA was analyzed for bacteria and fungi by amplifying 16S rRNA and ITS genes on the Illumina Miseq. Results indicated that Leptosphaerulina was the most abundant fungal genus present in the air vent and ground samples from HNM and HVM. At the same time, the most abundant bacterial genera in the air vent and ground samples were Propionibacterium and Streptococcus. The fungi community diversity was significantly different in the air vent samples. The abundance of fungal species known to be associated with respiratory diseases in indoor dust samples was similar, regardless of the visibility of fungi in the houses. The existence of fungi associated with respiratory symptoms was compared with several parameters like dust particulate matter (PM), CO2 level, temperature, and humidity. Most of these parameters are either positively or negatively correlated with the existence of fungi associated with respiratory diseases; however, none of these correlations were significant at p = 0.05. Our results indicate that implementing molecular methods for detecting indoor fungi may strengthen common exposure and risk assessment practices.

Metagenomic analysis unveils the microbial landscape of pancreatic tumors.

The composition of resident microbes in the human body is linked to various diseases and their treatment outcomes. Although studies have identified pancreatic ductal adenocarcinoma (PDAC)-associated bacterial communities in the oral and gut samples, herein, we hypothesize that the prevalence of microbiota in pancreatic tumor tissues is different as compared with their matched adjacent, histologically normal appearing tissues, and these microbial molecular signatures can be highly useful for PDAC diagnosis/prognosis. In this study, we performed comparative profiling of bacterial populations in pancreatic tumors and their respective adjacent normal tissues using 16S rRNA-based metagenomics analysis. This study revealed a higher abundance of Proteobacteria and Actinomycetota in tumor tissues compared with adjacent normal tissues. Interestingly, the linear discriminant analysis (LDA) scores unambiguously revealed an enrichment of Delftia in tumor tissues, whereas Sphingomonas, Streptococcus, and Citrobacter exhibited a depletion in tumor tissues. Furthermore, we analyzed the microbial composition between different groups of patients with different tumor differentiation stages. The bacterial genera, Delftia and Staphylococcus, were very high at the G1 stages (well differentiated) compared with G2 (well to moderate/moderately differentiated) and G3/G4 (poorly differentiated) stages. However, the abundance of Actinobacter and Cloacibacterium was found to be very high in G2 and G3, respectively. Additionally, we evaluated the correlation of programmed death-ligand (PDL1) expression with the abundance of bacterial genera in tumor lesions. Our results indicated that three genera such as Streptomyces, Cutibacterium, and Delftia have a positive correlation with PD-L1 expression. Collectively, these findings demonstrate that PDAC lesions harbor relatively different microbiota compared with their normal tumor adjacent tissues, and this information may be helpful for the diagnosis and prognosis of PADC patients.

Interrelation between Stress Management and Secretion Systems of Ralstonia solanacearum: An In Silico Assessment.

Ralstonia solanacearum (Rs), the causative agent of devastating wilt disease in several major and minor economic crops, is considered one of the most destructive bacterial plant pathogens. However, the mechanism(s) by which Rs counteracts host-associated environmental stress is still not clearly elucidated. To investigate possible stress management mechanisms, orthologs of stress-responsive genes in the Rs genome were searched using a reference set of known genes. The genome BLAST approach was used to find the distributions of these orthologs within different Rs strains. BLAST results were first confirmed from the KEGG Genome database and then reconfirmed at the protein level from the UniProt database. The distribution pattern of these stress-responsive factors was explored through multivariate analysis and STRING analysis. STRING analysis of stress-responsive genes in connection with different secretion systems of Rs was also performed. Initially, a total of 28 stress-responsive genes of Rs were confirmed in this study. STRING analysis revealed an additional 7 stress-responsive factors of Rs, leading to the discovery of a total of 35 stress-responsive genes. The segregation pattern of these 35 genes across 110 Rs genomes was found to be almost homogeneous. Increasing interactions of Rs stress factors were observed in six distinct clusters, suggesting six different types of stress responses: membrane stress response (MSR), osmotic stress response (OSR), oxidative stress response (OxSR), nitrosative stress response (NxSR), and DNA damage stress response (DdSR). Moreover, a strong network of these stress responses was observed with type 3 secretion system (T3SS), general secretory proteins (GSPs), and different types of pili (T4P, Tad, and Tat). To the best of our knowledge, this is the first report on overall stress response management by Rs and the potential connection with secretion systems.

Modulation of immune response in Ebola virus disease.

Ebola virus disease targets and destroys immune cells, including macrophages and dendritic cells, leading to impairment of host response. After infection, a combination of strategies including alteration and evasion of immune response culminating in a strong inflammatory response can lead to multi-organ failure and death in most infected patients. This review discusses immune response dynamics, mainly focusing on how Ebola manipulates innate and adaptive immune responses and strategizes to thwart host immune responses. We also discuss the challenges and prospects of developing therapeutics and vaccines against Ebola.

Corticosteroid Catabolism by Klebsiella pneumoniae as a Possible Mechanism for Increased Pneumonia Risk.

BACKGROUND: Several strains of Klebsiella pneumoniae are responsible for causing pneumonia in lung and thereby causing death in immune-suppressed patients. In recent year, few investigations have reported the enhancement of K. pneumoniae population in patients using corticosteroid containing inhaler. OBJECTIVES: The biological mechanism(s) behind this increased incidence has not been elucidated. Therefore, the objective of this investigating was to explore the relation between Klebsiella pneumoniae and increment in carbapenamase producing Enterobacteriaceae score (ICS). METHODS: The available genomes of K. pneumoniae and the amino acid sequences of steroid catabolism pathway enzymes were taken from NCBI database and KEGG pathway tagged with UniPort database, respectively. We have used different BLAST algorithms (tBLASTn, BLASTp, psiBLAST, and delBLAST) to identify enzymes (by their amino acid sequence) involved in steroid catabolism. RESULTS: A total of 13 enzymes (taken from different bacterial candidates) responsible for corticosteroid degradation have been identified in the genome of K. pneumoniae. Finally, 8 enzymes (K. pneumoniae specific) were detected in four clinical strains of K. pneumoniae. This investigation intimates that this ability to catabolize corticosteroids could potentially be one mechanism behind the increased pneumonia incidence. CONCLUSION: The presence of corticosteroid catabolism enzymes in K. pneumoniae enhances the ability to utilize corticosteroid for their own nutrition source. This is the first report to demonstrate the corticosteroid degradation pathway in clinical strains of K. pneumoniae.

Intrinsic role of bacterial secretion systems in phylogenetic niche conservation of Bradyrhizobium spp.

Bradyrhizobium is a biologically important bacterial genus. Different Bradyrhizobium strains exhibit distinct niche selection like free living, root nodular and stem nodular. The present in-silico study was undertaken to identify the role of bacterial secretome in the phylogenetic niche conservation (PNC) of Bradyrhizobium sp. Analysis was carried out with the publicly available 19 complete genome assembly and annotation reports. A protocol was developed to screen the secretome related genes using three different database, viz. genome, proteome and gene ortholog. This resulted into 139 orthologs that include type secretion systems (T1SS-T6SS) along with flagella (Flg), type IV pili (T4P) and tight adherence (Tad) systems. Multivariate analysis using bacterial secretome was undertaken to find out the role of these secretion systems in PNC. In free living strains, T3SS, T4SS and T6SS were completely absent. Whereas, in the stem nodulating strains, T3SS and T6SS were absent, but T4SS was found to be present. On the other hand, the T3SS was found to be present only in the root-nodulating strains. The present investigation clearly demonstrated a pattern of PNC based on the distribution of secretion system components. To the best of our knowledge, this is the first report on PNC of Bradyrhizobium using the multivariate analysis of secretome.

Recent advancement on chemical arsenal of Bt toxin and its application in pest management system in agricultural field.

Bacillus thuringiensis (Bt) is a Gram-positive, spore-forming, soil bacterium, which is very popular bio-control agent in agricultural and forestry. In general, B. thuringiensis secretes an array of insecticidal proteins including toxins produced during vegetative growth phase (such as secreted insecticidal protein, Sip; vegetative insecticidal proteins, Vip), parasporal crystalline δ-endotoxins produced during vegetative stationary phase (such as cytolytic toxin, Cyt; and crystal toxin, Cry), and ß-exotoxins. Till date, a wide spectrum of Cry proteins has been reported and most of them belong to three-domain-Cry toxins, Bin-like toxin, and Etx_Mtx2-like toxins. To the best of our knowledge, neither Bt insecticidal toxins are exclusive to Bt nor all the strains of Bt are capable of producing insecticidal Bt toxins. The lacuna in their latest classification has also been discussed. In this review, the updated information regarding the insecticidal Bt toxins and their different mode of actions were summarized. Before applying the Bt toxins on agricultural field, the non-specific effects of toxins should be investigated. We also have summarized the problem of insect resistance and the strategies to combat with this problem. We strongly believe that this information will help a lot to the budding researchers in the field of modern pest control biotechnology.

Is divalent magnesium cation the best cofactor for bacterial ß-galactosidase?

ß-Galactosidase is a metal-activated enzyme, which breaks down the glucosidic bond of lactose and produces glucose and galactose. Among several commercial applications, preparation of lactose-free milk has gained special attention. The present objective is to demonstrate the activity kinetics of ß-galactosidase purified from a non-pathogenic bacterium Arthrobacter oxydans SB. The enzyme was purified by DEAE-cellulose and Sephadex G-100 column chromatography. The purity of the protein was checked by high-performance liquid chromatography (HPLC). The purified enzyme of molecular weight ~95 kDa exhibited specific activity of 137.7 U mg-1 protein with a purification of 11.22-fold and yield 12.42%. The exact molecular weight (95.7 kDa) of the purified protein was determined by MALDI-TOF. Previously, most of the studies have used Mg+2 as a cofactor of ß-galactosidase. In this present investigation, we have checked the kinetic behavior of the purified ß-galactosidase in presence of several bivalent metals. Lowest Km with highest substrate (orthonitrophenyl- ß-galactoside or ONPG) affinity was measured in presence of Ca2+ (42.45 µM ONPG). However, our results demonstrated that Vmax was maximum in presence of Mn+2 (55.98 µM ONP produced mg-1 protein min-1), followed by Fe=2, Zn+2, Mg+2, Cu+2 and Ca+2. A large number of investigations reported Mg+2 as potential co factor for bgalacosidase. However, ß-galactosidase obtained from Arthrobacter oxydans SB has better activity in the presence of Mn+2 or Fe2+.

Evaluation of In Vivo Probiotic Efficiency of Bacillus amyloliquefaciens in Labeo rohita Challenged by Pathogenic Strain of Aeromonas hydrophila MTCC 1739.

Diseases in aquatic organisms, including fish, are a major concern in aquaculture production. In this present investigation, we have evaluated the beneficial effects of dietary Bacillus amyloliquefaciens CCF7 (GenBank Acc. No. KP256501) supplementation in rohu (Labeo rohita) challenged by a pathogenic strain of Aeromonas hydrophila MTCC 1739. Four experimental diets were formulated: control diet (no probiotics) and three experimental diets (different concentrations of probiotic candidate B. amyloliquefaciens CCF7 at 105 (T1), 107 (T2), 109 (T3) CFU/g). Further, we have divided the feeding trial into pre-challenge (70 days) and post-challenge (28 days) periods and various immune parameters (serum protein, globulin, albumin, lysozyme, and IgM), and stress parameters (malondialdehyde, catalase, and superoxide dismutase) were examined during both the periods. Throughout the entire experiment, control group was fed with probiotic free basal diet, while the treatment groups received probiotic supplemented diets (PSD). After challenge test, serum aspartate transaminase (AST), serum alanine transaminase (ALT) activity, and liver malondialdehyde level have increased significantly in control groups; however, level of these parameters were considerably lower in fish fed with PSD. In contrast, liver catalase and superoxide dismutase activities and serum globulin concentration was significantly higher in the group fed with T3 diet followed by T2. Furthermore, an elevated level of serum IgM and higher activity of serum lysozyme was also recorded in PSD fed groups, especially for T3 group which confirmed the probiotic efficiency of the bacterium B. amyloliquefaciens CCF7. We strongly believe that B. amyloliquefaciens CCF7 will be a good probiotic candidate in aquaculture industries.

Quorum-sensing network-associated gene regulation in Gram-positive bacteria.

Quorum sensing (QS) is the chemical communication processes between bacteria, which may be inter-genus or intra-genus. In general, several physiological functions, such as nutrient uptake, competence development, biofilm formation, sporulation, and toxin secretion, are accomplished through QS process. The QS (cell density-dependent process) circuit in Gram-positive bacteria consists mainly of two parts: an inducer molecule and a receptor protein. The binding of inducer molecule to receptor activates the target gene, which then performs the necessary function in bacteria. In the past few years, several investigations have been conducted to explore the QS circuit in various bacteria, but still this information is insufficient to fully understand the bacterial gene expression cascade. In the present review, we summarize the QS architecture and their associated gene regulation in four Gram-positive bacteria, such as Bacillus subtilis, Staphylococcus aureus, Bacillus cereus, and Streptococcus pneumoniae. It is well established that S. aureus, B. cereus, and S. pneumoniae are potent human pathogen. A detailed understanding of QS circuit in these bacteria would be useful in preparation of customized medicine in future. Whereas, B. subtilis is an industrially important candidate and has been used in several biotechnology sectors. Understanding of QS circuit in B. subtilis will definitely enrich the antibiotics and enzyme industries.