Acetic acid resistance

Various protein production changes are also known to be implicated in the development of resistance to acetic acid. One important protein that has been identified is now known as "aconitase." It may also be possible that there exists some other mechanism, located in the bacterial cell membrane by which acetic acid resistance is conferred, as it is known that acetic acid causes toxicity by acting as an uncoupling agent, which would disturb the proton motive force. The presence of such a proton motive efflux system for acetic acid is present in A. acetii (Matsushita et al., 2005). 

It is, however, unclear if it contributes to acetic acid resistance in acetic fermentation (Nakano, Fukaya, and Horinouchi, 2006). 

In A. acetii a defect in the membrane-bound alcohol dehydrogenase has also been associated with a reduction in acetic acid resistance, implicating this enzyme in the development of resistance to this acid. It has also been found that resistance to acetic acid does not always result from resistance to low pH, as strains previously able to grow at a low pH cannot grow when the pH is decreased as a result of acetic acid (Nakano, Fukaya, and Horinouchi, 2006). 

Nakano, S., Fukaya, M., and Horinouchi, S. 2006. Putative ABC transporter responsible for acetic acid resistance in Acetobacter aceti. Applied and Environmental Microbiology 72 497-505. 

Trcek, J., Toyama, H., Czuba, J., Misiewicz, A., and Matsushita, K. 2006. Correlation between acetic acid resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria. Applied Microbiology and Biotechnology 70 366-373. 

Acetic acid bacteria are naturally highly resistant to acetic acid, with notable differences in tolerance between species (Trcek et al., 2006). The enzyme AatA plays an important role in acetic acid resistance in these... 

Other mechanisms conferring acetic acid resistance are also located in the cell membrane, because the toxicity of organic acids may be partly a result of a disruption of the proton motive force by acetic acid, acting as an uncoupling agent. A proton motive efflux system for acetic acid has also recently been described in A. acetii (Matsushita et al., 2005). Mutation and overexpression of the aatA gene also caused resistance to formic and propionic acids simultaneously to that of acetic acid. aatA functions as an efflux pump of acetic acid. Several transporters for monocarboxylic acids are known (Nakano, Fukaya, and Horinouchi, 2006) ... 

However, these transporters do not contain any ABC motifs and transport monocarboxylic acids via a proton-coupled reaction. Acetic acid resistance in A. acetii is, therefore, conferred by at least two mechanisms assimilation of the weak acid by enzymes, such as citrate synthase or aconitase and export of acetic acid by ABC transporter. Both mechanisms are implicated in reducing intracellular acetic acid concentration (Nakano, Fukaya, and Horinouchi, 2006). 

Acetic acid resists to a high degree the action of oxidizing agents. Its stability under these circumstances is so great that it is often used as a solvent for substances which are to be oxidized by chromic acid. 

Bacteria. - P NMR has been used to investigate Zymomonas mobilis ZM4/Ac", an acetic acid resistant strain of Z. mobilis ZM4, to determine the possible mechanisms of resistance to acetic acid. The mutant strain showed... 

Whole-genome sequences of the highly acetic acid-resistant bacteria K. europaeus as the reference strain and a strain of K. oboediens isolated from vinegar fermentation were reported (Andres-Barrao et al. 2011). The genome sequence was also completed for Gluconacetobacter sp. strain SXCC-1 isolated from the starter of Chinese Shanxi vinegar (Du et al. 2011). 

The membrane-bound PQQ-alcohol dehydrogenase (ADH) is to be considered the key enzyme in the production of vinegar because of its essential place in the oxidation of ethanol to acetaldehyde, the intermediate that will be later oxidized by the MCD (molybdopterin cytosine dinucleotide)-aldehyde dehydrogenase (ALDH) to acetic acid. This idea is based on the finding that a defect in membrane-bound ADH has been associated with a reduction in acetic acid resistance (Chinnawirotpisan et al. 2003 Okumura et al. 1985 Takemura et al. 1991). Additionally, the elevation in membrane-bound ALDH activity by gene amplification has been reported to enhance the acetic acid concentration finally attained in Acetobacter (Fukaya et al. 1989). 

A direct link has been established between acetic acid resistance and the capability to oxidize ethanol during the diauxic growth curve in AAB (Ohmori et al. 1982). The PQQ-ADH activity in Komagataeibacter strains reached higher values (at least twice as high) than those in Acetobacter, under the same growth conditions (Trcek et al. 2006, 2007). 

Role of Plasmids Involved in Acetic Acid Resistance... 

Fukaya M, Takemura H, Tayama K, Okumura H, Kawamura Y, Horinouchi S, Beppu T (1993) The aaiC gene responsible for acetic acid assimilatirai confers acetic acid resistance on Acetobacter aceti. J Ferment Bioeng 76(4) 270-275 Gerdes K (2000) Toxin-antitoxin modules may regulate synthesis of macromolecules during nutritional stress. J Bacteriol 182 561-572... 

Kanchanarach W, Theeragool G, Inoue T, Yaknshi T, Adachi O, Matsushita K (2010) Acetic acid fermentation of Acetobacter pasteurianus relationship between acetic acid resistance and pellicle polysaccharide formation. Biosci Biotechnol Biochem 74(8) 1591-1597 Kaneshiro T, Law JH (1964) Phosphatidylcholine synthesis in Agrobacterium tumefaciens. I. Purification and properties of a phosphatidylethanolamine N-methyltransferase. J Biol Chem 239 1705-1713... 

Takemura H, Horinouchi S, Beppu T (1991) Novel insertion sequence IS1380 from Acetobacter pasteurianus is involved in loss of ethanol-oxidizing ability. J Bacteriol 173(22) 70-76 Trcek J (2015) Plasmid analysis of high acetic acid-resistant bacterial strains by two-dimensional agarose gel electrophoresis and insights into the phenotype of plasmid pJK2-l. Ann Microbiol 65(3) 1287-1292... 

Trcek J, Barja F (2015) Updates on quick identification of acetic acid bacteria with a focus on the 16S-23S rRNA gene internal transcribed spacer and the analysis of cell proteins by MALDI-TOF mass spectrometry. Int J Food Microbiol 196 137-144 Trcek J, Raspor P, Teuber M (2000) Molecular identification of Acetobacter isolates fiom submerged vinegar production, sequence analysis of plasmid pJK2-l and application in development of a cloning vector. Appl Microbiol Biotechnol 35 1899-1901 Trcek J, Toyama H, Czuba J, Misiewicz A, Matsushita K (2006) Correlation between acetic acid resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria. Appl Microbiol Biotechnol 70(3) 366-373... 

Physiology of Acetobacter and Komagataeibacter spp. Acetic Acid Resistance Mechanism in Acetic Acid Fermentation... 

Fig. 10.9 Schematic representation of molecular machineries that confer acetic acid resistance in Acetobacter and Gluconacetobacter. (Schematic diagram quoted from Nakano and Fukaya 2008) THBH and phosphatidylcholine on the membrane and polysaccharide on the surface of the cells are suggested to be involved in acetic acid resistance. Acetic acid, which penetrates into the cytoplasm, is assumed to be metabolized through the TCA cycle by the actions of enzymes typical for AAB. Furthermore, intracellular acetic acid is possibly pumped out by a putative ABC transporter and proton motive force-dependent efflux pump using energy produced by ethanol oxidation or acetic acid overoxidation. Intracellular cytosolic enzymes are intrinsically resistant to low pH and are protected against denaturation by stress proteins such as molecular chaperones. ADH membrane-bound alcohol dehydrogenase, ALDH membrane-bound aldehyde dehydrogenase, CS citrate synthase, ACN aconitase, PC phosphatidylcholine...

---