Secretome analysis of alkaliphilic bacterium Bacillus lehensis G1 in response to pH changes

Abstract

Bacillus lehensis G1 is an alkaliphilic bacterium that is capable of surviving in environments up to pH 11. Secretome related to bacterial acclimation in alkaline environment has been less studied compared to cytoplasmic and membrane proteome. The aim of this study was to gain better understanding of bacterial acclimation to alkaline media through analyzing extracellular proteins of B. lehensis. The pH range for B. lehensis growth was conducted, and two-dimensional electrophoresis and MALDI-TOF/TOF MS analysis were conducted to characterize changes in protein profiling in B. lehensis cultured at pH 8 and pH 11 when compared with those cultured at pH 10 (optimal growth pH). B. lehensis could grow well at pH ranging from 8 to 11 in which the bacteria showed to posses thinner flagella at pH 11. Proteomic analyses demonstrated that five proteins were up-regulated and 13 proteins were down-regulated at pH 8, whereas at pH 11, 14 proteins were up-regulated and 8 were down-regulated. Majority of the differentially expressed proteins were involved in the cell wall, main glycolytic pathways, the metabolism of amino acids and related molecules and some proteins of unknown function. A total of 40 differentially expressed protein spots corresponding to 33 proteins were identified; including GlcNAc-binding protein A, chitinase, endopeptidase lytE, flagellar hook-associated proteins and enolase. These proteins may play important roles in acclimation to alkaline media via reallocation of cell wall structure and changes to cell surface glycolytic enzymes, amino acid metabolism, flagellar hook-associated proteins and chaperones to sustain life under pH-stressed conditions.

Bacillus miscanthi sp. nov., a alkaliphilic bacterium from the rhizosphere of Miscanthus sacchariflorus

“…For phenotypic characterization, the cellular morphology and motility of strain AK13 T were observed by phase-0contrast microscopy (Carl Zeiss). Growth rates on LB medium (pH 8) at different temperatures (5, 10,12,14,16,18,20,22,24,26,28,30,32,34,35, 37 or 40 °C), pH (6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5 or 13) and sodium salt (NaCl) concentrations (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13 %) were measured after 2 days of culture. The pH values of the LB media were adjusted with HCl and KOH after the sterilization of the media at 0.15 MPa and 121 °C for 15 min.…”

“…Unlike the transmission electron microscopy results, which were concerned with the cells cultured in LB medium, flagella were not detected by FE-SEM (). This result is possibly because flagella-associated genes, such as flagellar basal body ( fliZPQR, flhBAF ), filaments ( flaB ) and hook genes ( fliD , flgKL ) in strain AK13 T were not substantially expressed under the latter experimental conditions [27, 28]. The same initial inoculum of Bacillus species was grown in LB media adjusted to pH 8, which was monitored at 30 °C for up to 5 days without agitation.…”

Adaptation of neutrophilic Paracoccus denitrificans to denitrification at highly alkaline pH

“…In Escherichia coli, the Na/H transporter also plays a role in detecting pH changes (Krulwich et al 2011). Then, at alkaline pH, several pH regulation systems, such as the membrane transporters Na/H or K/H or drugs/H, would be stimulated (Padan et al 2005;Ling et al 2018). To adapt to long-term environmental change, new adaptive mechanisms can emerge by means of spontaneous mutations acquired over generations and selected in response to the environmental pH pressure.…”

“…-Modifications of the cell wall to shift the permeability to protons (Horikoshi 1999;Preiss et al 2015;Ling et al 2018).…”

Influence of Hydrogen Electron Donor, Alkaline pH, and High Nitrate Concentrations on Microbial Denitrification: A Review

“…Amino acid substitutions were also observed on various enzymes not necessarily involved in respiration, allowing them to operate efficiently at alkaline pH [119]. The optimal pH for proteins of alkaliphilic bacteria is, therefore, higher than those of neutrophilic bacteria.…”