Vibrio cholerae O1 Strain TSI-4 Produces the Exopolysaccharide Materials That Determine Colony Morphology, Stress Resistance, and Biofilm Formation

Abstract

Vibrio cholerae O1 strain TSI-4 (El Tor, Ogawa) can shift to a rugose colony morphology from its normal translucent colony morphology in response to nutrient starvation. We have investigated differences between the rugose and translucent forms of V. cholerae O1 strain TSI-4. Electron microscopic examination of the rugose form of TSI-4 (TSI-4/R) revealed thick, electron-dense exopolysaccharide materials surrounding polycationic ferritin-stained cells, while the ferritin-stained material was absent around the translucent form of TSI-4 (TSI-4/T). The exopolysaccharide produced byV. cholerae TSI-4/R was found to have a composition ofN-acetyl-d-glucosamine,d-mannose, 6-deoxy-d-galactose, andd-galactose (7.4:10.2:2.4:3.0). The expression of an amorphous exopolysaccharide promotes biofilm development under static culture conditions. Biofilm formation by the rugose strain was determined by scanning electron microscopy, and most of the surface of the film was colonized by actively dividing rod cells. The corresponding rugose and translucent strains were compared for stress resistance. By having exopolysaccharide materials, the rugose strains acquired resistance to osmotic and oxidative stress. Our data indicated that an exopolysaccharide material on the surface of the rugose strain promoted biofilm formation and resistance to the effects of two stressing agents.

How Vibrio cholerae survive during starvation

“…In our studies [31,32], V. cholerae O1 strain TSI-4 and V. cholerae O139 strain MO10 could shift to a rugose colony morphology ( Fig. 1) associated with the expression of amorphous extracellular polysaccharides (EPSs) in response to nutrient starvation.…”

“…Global regulatory mechanisms also adjust EPS synthesis according to the general physiological status of the cell, turning it up under nutritional de¢ciency states or down when carbon and energy must be diverted to growth and repair processes. We have also observed that V. cholerae O1 strain TSI-4 and O139 strain MO10 underwent phase variation, converting from translucent to rugose in M9 salts and back again at a frequency of 1.5U10 35 in L broth [31,32]. These bidirectional switches between the two colony types would favor outgrowth of the variant best adapted to a particular environment.…”

“…The persistence of viable cholera organisms may then further spread of the infection. The V. cholerae rugose phenotype represents a fully virulent survival form of the organism [44] that can persist in the natural environment by using its ability to form bio¢lms [31,32].…”

“…It may also provide protection from natural environmental oxidants. The rugose variant is relatively resistant to H 2 O 2 [31]. The cells of V. cholerae demonstrate a predilection for association with chitinaceous surfaces, the mucilaginous sheath of algae and copepods that can be interpreted as an ecologic advantage [46^49].…”

Regulation of biofilm formation and cellular buoyancy through modulating intracellular cyclic di‐GMP levels in engineered cyanobacteria

“…In cyanobacteria high irradiance of BL may cause photodamage (Ohnishi et al, 2005), but strong BL could not cause photoinhibition when cyanobacteria cells were embedded in a biofilm (Hsieh et al, 2014). In addition to providing protection from BL, biofilms can support the scavenging of reactive oxygen species from the surrounding environment (Bylund et al, 2006), and reduce oxidative stress through altering the structural integrity or surface electrical charge of microbial community structure (Chen et al, 2004;Wai et al, 1998).…”