A quantitative study of gene regulatory pathways in Bacillus subtilis for virulence and competence phenotype by quorum sensing

Influence of Oral Administration of Bacillus subtilis on Growth Performance and Physiological Responses in Litopenaeus vannamei Cultured in Low Saline Waters

The present study examined the effect of Bacillus subtilis on growth performance, digestive enzyme activity, and immune response of juvenile white-leg shrimp (Litopenaeus vannamei) in 100 m² lined ponds. Control (without B. subtilis) and experimental (with B. subtilis) diets were fed at 10% of animal body weight, four times daily for 6 weeks in duplicate ponds. Significantly increased final weight, weight gain, specific growth rate, average daily growth, and survival rate were observed in the B. subtilis treated group (P < 0.05). Significantly higher (P < 0.05) digestive enzyme activities of protease, lipase, amylase, and cellulase were found in the B. subtilis supplemented diet fed group. At the end of trial, a challenge study, using Vibrio alginolyticus, found lower (15.00 ± 2.88%) cumulative mortality in the B. subtilis treated group compared to control (73.33 ± 3.33%). Activities of immune and antioxidant enzymes (phenoloxidase, SOD, and catalase) were significantly higher (P < 0.05) in the B. subtilis-incorporated diet fed group. Interestingly, histopathology of the hepatopancreas and intestine revealed that the B. subtilis-supplemented group showed no deformity. Overall, the study found inclusion of B. subtilis in P. vannamei diet improves growth, physiometabolic activities, and immunity, indicating B. subtilis as a potential probiotic for shrimp feed.

Fungal-bacterial interaction selects for quorum sensing mutants with increased production of natural antifungal compounds

Soil microorganisms coexist and interact showing antagonistic or mutualistic behaviors. Here, we show that an environmental strain of Bacillus subtilis undergoes heritable phenotypic variation upon interaction with the soil fungal pathogen Setophoma terrestris (ST). Metabolomics analysis revealed differential profiles in B. subtilis before (pre-ST) and after (post-ST) interacting with the fungus, which paradoxically involved the absence of lipopeptides surfactin and plipastatin and yet acquisition of antifungal activity in post-ST variants. The profile of volatile compounds showed that 2-heptanone and 2-octanone were the most discriminating metabolites present at higher concentrations in post-ST during the interaction process. Both ketones showed strong antifungal activity, which was lost with the addition of exogenous surfactin. Whole-genome analyses indicate that mutations in ComQPXA quorum-sensing system, constituted the genetic bases of post-ST conversion, which rewired B. subtilis metabolism towards the depletion of surfactins and the production of antifungal compounds during its antagonistic interaction with S. terrestris.

Reprogramming Probiotic Lactobacillus reuteri as a Biosensor for Staphylococcus aureus Derived AIP-I Detection

Gram-positive Staphylococcus aureus infection that results in pneumonia, urinary tract infection, and in severe cases, sepsis, has recently been classified as a serious threat to public health. Rapid and cost-effective detection of these infections are costly and time-consuming. Here, we present probiotic lactic acid bacteria engineered to detect autoinducer peptide-I (AIP-I), a quorum sensing molecule produced by Staphylococcus sp. during pathogenesis. We achieved this by adapting the well-characterized agr quorum sensing ( agrQS) from Staphylococcus aureus into Lactobacillus reuteri. The engineered biosensor is able to detect AIP-I levels in the nanomolar to micromolar range. We further investigated the function of the biosensor to detect real-time changes in AIP-I levels to understand the dynamics of Staphylococcus aureus under various strenuous conditions. The developed sensors would be useful for detection of Staphylococcus contamination in hospital settings and for high-throughput drug screening.

NMDB: NETWORK MOTIF DATABASE ENVISAGED AND EXPLICATED FROM HUMAN DISEASE SPECIFIC PATHWAYS

The study of network motifs for large number of networks can aid us to resolve the functions of complex biological networks. In biology, network motifs that reappear within a network more often than expected in random networks include negative autoregulation, positive autoregulation, single-input modules, feedforward loops, dense overlapping regulons and feedback loops. These network motifs have their different dynamical functions. In this study, our main objective is to examine the enrichment of network motifs in different biological networks of human disease specific pathways. We characterize biological network motifs as biologically significant sub-graphs. We used computational and statistical criteria for efficient detection of biological network motifs, and introduced several estimation measures. Pathways of cardiovascular, cancer, infectious, repair, endocrine and metabolic diseases, were used for identifying and interlinking the relation between nodes. 3–8 sub-graph size network motifs were generated. Network Motif Database was then developed using PHP and MySQL. Results showed that there is an abundance of autoregulation, feedforward loops, single-input modules, dense overlapping regulons and other putative regulatory motifs in all the diseases included in this study. It is believed that the database will assist molecular and system biologists, biotechnologists, and other scientific community to encounter biologically meaningful information. Network Motif Database is freely available for academic and research purpose at: http://www.bioinfoindia.org/nmdb .