Coculture communities of microbes are more realistic and common in nature than in laboratory-grown pure cultures. In a mixed community, when resources with a potential role in growth are shared, conflict (as a consequence of competition) or cooperation is certain. In our study, this situation of conflict and cooperation was explored to understand the population dynamics and community behavior of Listeria monocytogenes. The social behavioral response of L. monocytogenes to the presence of Bacillus subtilis was studied in terms of divergence in gene expression of L. monocytogenes. It is evident from the results that social behavior of L. monocytogenes changes from competition for survival in broth to cooperation and coexistence in biofilm. Furthermore, the gene expression pattern is clearly indicative of L. monocytogenes switching from aerobic to fermentative metabolism in broth and biofilm conditions, respectively.

This paper reports a rapid microwave biosensor to check forEscherichia coli contamination in water samples, which can thereafter be extended for testing of other microbes as well. The sensor is a 3x3 array of polystyrene cylinders 8 of which are filled with poly vinyl chloride solid cylinders with the centre hollow cylinder holding the sample to be investigated. The sensor takes only 4-5 minutes for sensitive detection of up to 1-2 Colony forming units (CFU) of Escherichia coli. The present technique thus proves better than all presently available techniques in terms of both sensitivity and resolution and speeds up the detection process manifold. Microwave bio-sensing thus presents itself as a promising solution for rapid, sensitive and user-friendly detection of water contamination.

Majority of studies concerning the gene expression of Listeria monocytogenes have been done on pure culture states. Our objective was to study L.monocytogenes in a co-cultured state and to understand if microbes in their natural state of existence are different in their expression than that of the purely cultured lab grown forms. For a long period discussions have been on the expression of prfA, (which is a virulence gene regulator) in a mammalian host and its role in causing the switch from a saprophytic to pathogenic form of L.monocytogenes. We, in this paper for the first time report the expression of prfA and other virulence genes by L.monocytogenes under different extracellular conditions, and also as a pure culture biofilms, that is different from the previous reports. We also report that the expression of prfA seems to vary considerably when co-cultured with Bacillus subtilis.

Problem statement: Do naturally group-living bacteria express genes the same way as they do in lab grown pure cultures? An intriguing question. Listeria monocytogenes, a dreaded pathogen has been and continues to be a subject of study with reference to gene expressions. However, all studies concerning the gene expression of L. monocytogenes have been done on pure culture states. Our objective was to study L. monocytogenes in a co-cultured state and thereby substantiate that microbes in their natural state of existence are different in their expression than that of the purely cultured lab grown forms. Approach: In this study we have focused on the transcriptional and growth response of L. monocytogenes to the presence of Bacillus subtilis to its niche as planktonic cells and in biofilms. Transcriptional response with reference to Antibiotic Resistance and Synthesis, was studied to elaborate on the differences in gene expression in L. monocytogenes as planktonic cells and in biofilm, co-cultured with B. subtilis. Results: Majority of genes responsible for antibiotic resistance that were up-regulated in co-cultured broth were down regulated in co-cultured biofilm. Conclusion: Our observation provides evidence to L. monocytogenes being suppressed by B. subtilis, however in Biofilms both the species seemed to cooperate with each other towards community living.

In this paper, we used the distinguishable surface charge and mass of different bacterial strains for label free detection and differentiation of pathogen through impedance and magnetohydrodynamic (MHD) analysis. For the isolation of Escherichia coli and Staphylococcus aureus, functionalized magnetic nanoparticles (MNPs) were used. The proposed method is aimed at minimizing extensive chemical preparation and labor intensive conventional microbiological processing thereby reducing the detection time. Pathogens isolated from broth cultures using the MNPs were subjected to impedance rate measurement through an arduino-based automated impedance sensor along with differentiation on the basis of Larmor's motion through the MHD approach. The proposed method evidently reports that the two bacterial species bind differently to the MNPs giving appreciable variation in the impedance rate increment for a dc electric field of 250V/m. In addition to this, cross-field drift through 171.4 V/m electric field and a normal magnetic field of 500 Gauss led to lump formation in S. aureus but had no such effect on E. coli. The mobility analysis of the two species of bacteria was also carried out by observing the gyration of bacteria through naked eyes. The mobility of lumped bodies of S. aureus was of the order 10 m/V sec; whereas for dispersed E. coli, it was 10 m/V sec.