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Unravelling the multiple effects of lactic acid stress on Lactobacillus plantarum by transcription profiling

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Author: Pieterse, B. · Leer, R.J. · Schuren, F.H.J. · Werf, M.J. van der
Type:article
Date:2005
Institution: TNO Kwaliteit van Leven
Source:Microbiology, 12, 151, 3881-3894
Identifier: 238901
doi: doi:10.1099/mic.0.28304-0
Keywords: Biology · Biotechnology · lactic acid · article · bacterial genome · bacterial growth · concentration (parameters) · controlled study · culture medium · DNA microarray · gene expression profiling · gene identification · gene sequence · genetic code · genetic transcription · growth rate · lactic acid bacterium · Lactobacillus plantarum · nonhuman · nucleotide sequence · open reading frame · osmolarity · priority journal · RNA isolation · steady state · Bioreactors · Fermentation · Gene Expression Profiling · Gene Expression Regulation, Bacterial · Genes, Bacterial · Hydrogen-Ion Concentration · Lactic Acid · Lactobacillus plantarum · Transcription, Genetic · Bacteria (microorganisms) · Lactobacillus plantarum

Abstract

The organic acid lactate is the predominant fermentation product of Lactobacillus plantarum. The undissociated form of this organic acid is a strong growth inhibitor for the organism. Different theories have been postulated to explain the inhibitory effects of lactic acid: (i) toxicity arising from the dissipation of the membrane potential, (ii) acidification of the cytosol, or (iii) intracellular anion accumulation. In general, organic acid stresses are complex to study, since their toxicity is highly dependent on their degree of dissociation and thus on the pH. In this study, transcription profiles of L. plantarum grown in steady-state cultures that varied in lactate/lactic acid concentration, pH, osmolarity and absolute and relative growth rate, were compared by microarray analysis. By doing so, the differential expression of multiple groups of genes could specifically be attributed to the different aspects of lactic acid stress. A highly coherent group of lactic acid- responsive, cell surface protein-encoding genes was identified, to which no function has previously been assigned. Moreover, a group of genes that showed increased expression in response to the combination of lactic acid and a lower growth rate is expected to be involved in the formation of the alternative fermentation end-products malate, acetate and ethanol. One of these pathways is the phosphoketolase by-pass that is typical for bifidobacteria. © 2005 SGM.