Department of Biological Sciences
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Item Insights Into the Dynamics and Composition of Biofilm Formed by Environmental Isolate of Enterobacter cloacae(Frontiers, 2022-07) Jha, Prabhat Nath; Tare, MeghanaBacterial biofilms are clinically admissible and illustrate an influential role in infections, particularly those related to the implant of medical devices. The characterization of biofilms is important to understand the etiology of the diseases. Enterobacter cloacae are known for causing infections by forming biofilms on various abiotic surfaces, such as medical devices. However, a detailed characterization in terms of morphology and the molecular composition of the formed biofilms by this bacterium is sparse. The present study provides insights into the biofilm formation of E. cloacae SBP-8, an environmental isolate, on various surfaces. We performed assays to understand the biofilm-forming capability of the SBP-8 strain and characterized the adhering potential of the bacteria on the surface of different medical devices (foley latex catheter, enteral feeding tube, and glass) at different temperatures. We found that medical devices exhibited strong colonization by E. cloacae SBP-8. Using field emission-scanning electron microscopy (FE-SEM) studies, we characterized the biofilms as a function of time. It indicated stronger biofilm formation in terms of cellular density and EPS production on the surfaces. Further, we characterized the biofilm employing surface-enhanced Raman spectroscopy (SERS) and identified the vast heterogenic nature of the biofilm-forming molecules. Interestingly, we also found that this heterogeneity varies from the initial stages of biofilm formation until the maturation and dispersion. Our studies provide insights into biofilm composition over a period of time, which might aid in understanding the biofilm dispersion phases, to enhance the presently available treatment strategies.Item Characterizing the type 6 secretion system (T6SS) of E. cloacae SBP-8 and its role in pathogenesis and bacterial competition(Elsevier, 2023-10) Jha, Prabhat Nath; Marathe, SandhyaDespite the relevance of E. cloacae as an opportunistic pathogen, very little is known about its pathogenicity mechanism and the factors influencing its virulence. The mechanism of E. cloacae pathogenicity appears to be complex and multifactorial, with the presence of different putative virulence factors whose role is still not clear in the development of the disease. In this study, we systematically investigated the role of T6SS (type six secretion system) of E. cloacae SBP-8, an environmental isolate, in eukaryotic and bacterial cell interaction. Analysis of the genome sequence of E. cloacae SBP-8 revealed the presence of sets of genes coding for the expression of one complete T6SS cluster, which is similar to T6SS-1 cluster of E. cloacae ATCC 13047 (clinical isolates). In addition, an Hcp effector protein was detected in the secretome, and this secretion depended on ClpV, an Atpase of T6SS, confirming that strain SBP-8 produces functional T6SS. Deletion of T6SS-associated gene clpV did not induce any significant change in the life span and rate of colonization in C. elegans. No major significant change was observed in the expression profiling of antimicrobial genes (clec-60, clec-85, clec-87 and lys-1) and toll-like receptor (toll-1) gene, involved in stimulating an immune response against the pathogen. No difference in the ability to invade and proliferate in intestinal cells and phagocytosis by macrophages was observed. In addition, we demonstrated that the ability of E. cloacae SBP-8 to out-compete Escherichia coli was reliant upon its T6SS in contact-dependent manner. Our results show that T6SS of the environmental isolates is required for interbacterial competition but not for invasion and proliferation inside host cells.