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

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... ural 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.