Phenotypic Switching in Biofilm-Forming Marine Bacterium Paenibacillus lautus NE3B01
Biofilm-forming marine bacterium Paenibacillus lautus NE3B01 was isolated from a mangrove ecosystem, Odisha, India. This isolate formed a swarming type of colony pattern on the solid culture medium with 0.5–2 % agar. Phase contrast microscopy study of a growing colony of P. lautus on solid media and swarming pattern revealed the existence of two phenotypically distinct cells (i.e. cocci and rods) across the colonies. However, in actively growing planktonic culture, only rod-shaped cells were observed. Biofilm growth studies (crystal violet assay) with the isolate showed significant biofilm formation by 6 h, and the detachment phase was observed after 18 h. Biofilm parameters (such as total biomass, roughness coefficient, biofilm thickness, etc.) of 24-h-old P. lautus biofilm were studied by confocal scanning laser microscopy (CSLM). The CSLM study showed that P. lautus formed a biofilm with an average thickness of 14.8 ± 2.6 μm, a high roughness coefficient (0.379 ± 0.103) and surface to bio-volume ratio (4.59 ± 1.12 μm2/μm3), indicating a highly uneven topography of the biofilm. This also indicates that the 24-h-old biofilm is in dispersal phase. Scanning electron microphotographs of P. lautus also supported the existence of two distinct phenotypes of P. lautus. The current findings suggest that P. lautus has two vegetative phenotypes and to decongest the overcrowded biofilm the bacterium can switch over to motile rods from nonmotile cocci and vice versa.
KeywordsPhenotypic Switching Coccoid Cell Confocal Scanning Laser Microscopy Study Detachment Phase Biovolume Ratio
The authors would like to acknowledge the authorities of NIT, Rourkela and BARC Facilities, Kalpakkam for providing facilities. N.M. gratefully acknowledges the receipt of fellowship from Ministry of Human Resource Development, Government of India for doctoral research. S.D. thanks the Department of Biotechnology, Government of India for research grants on biofilm-based enhanced bioremediation.
Conflicts of interest
Authors of the manuscript declare no conflict of interest.
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