A high cell wall negative charge is necessary for the growth of the alkaliphile Bacillus lentus C-125 at elevated pH

Abstract

The structural components in cell walls of three mutants of a facultative alkaliphile, Bacillus lentus C-125, defective in certain cell-wall components were characterized in detail. The cell walls of the wild-type C-125 were thick and increased in thickness when grown at high pH. Electron microscopy showed that triple layers developed when the bacteria were grown in an alkaline environment. In contrast, cell walls of teichuronopeptide (1UP)-defective mutants consisted of a single layer. For both the wild-type and mutants, the cell-wall concentrations o f the acidic structural polymers teichuronic acid and TUP increased with respect to peptidoglycan as culture pH increased. For all four strains, the anion content of their cell walls was the greatest at high pH. The cell-wall density of the negatively charged compounds (uronic acids plus L-glutamic acid) was calculated as about 3 and 9 equivalents (I cell wall region)-' for C-125 cells grown at pH 7 and 10, respectively. A t high pH, the specific growth rates of the two TUPdefective mutants were much lower than those of the wild-type. It is concluded that increased levels of acidic polymers in the cell walls of alkaliphilic bacteria may be a necessary adaptation for growth at elevated pH.

Two-Dimensional Gel Electrophoresis Analyses of pH-Dependent Protein Expression in Facultatively AlkaliphilicBacillus pseudofirmusOF4 Lead to Characterization of an S-Layer Protein with a Role in Alkaliphily

“…The role of the B. pseudofirmus OF4 SlpA in alkaliphily is somewhat analogous to that proposed for the cell wall teichuronopeptide in B. halodurans C-125 (3)(4)(5)21). Neither of these cell wall polymers in the two different alkaliphiles is essential for alkaliphily, but both are involved in supporting the Na ϩ -dependent pH homeostasis that principally relies upon active transport mechanisms.…”

“…Net proton as well as solute uptake is coupled to this cycle. Work on B. halodurans C-125 has shown that in addition to the critical role of the active transporters of the Na ϩ cycle, acidic cell surface polymers contribute to pH homeostasis and alkaliphily, in particular a teichuronopeptide that is more highly expressed at high pH then at low pH (3)(4)(5). By contrast, B. pseudofirmus OF4 did not appear to possess these acidic polymers (18).…”

Alkaliphiles

“…It is reported that the amount of acidic polymers increases during growth under alkaline pH conditions. 16) A pH-homeostatic mechanism for alkaliphilic bacteria has been proposed taking the important role of anionic polymer layer in their cell walls into account. Donnan equilibria in the bacterial cell walls were calculated to estimate the pH values inside the polymer layer of the cell walls when the outer aqueous solution is in alkaline nature.…”

Decrease in Cytoplasmic pH-Homeostastatic Activity of the AlkaliphileBacillus LentusC-125 by a Cell Wall Defect

“…At this pH, C-125 grows well and develops the homeostatic activity well although C-125-90 grows poorly. 15,17) The cytoplasmic pH of each derivative exposed to pH lower than 9 was almost the same as that of the parent (Fig. 1).…”

“…Cell-wall densities of negatively charged compounds, such as glutamic and glucuronic acids, are 6.7, 6.0, 4.0 and 4.1 mmol W mg of peptidoglycan in C-125, C-125-11, C-125-F19 and C-125-90 grown at pH 10, respectively. 17) Thus, it is likely that the intensity of the pHhomeostatic activity and abundance of the acidic constituents are correlated in the cells grown at pH 10.…”