Adaptation of Microorganisms to Cold Temperatures, Weak Acid Preservatives, Low pH, and Osmotic Stress: A Review

Abstract

The application of physical stress to microorganisms is the most widely used method to induce cell inactivation and promote food stability. To survive, microorganisms have evolved both physiological and genetic mechanisms to tolerate some extreme physical conditions. This is clearly of significance to the food industry in relation to survival of pathogens or spoilage organisms in food. In some microorganisms, the "cold shock response" has been observed in response to abrupt changes to lower temperatures. This results in the production of specific sets of proteins (cold shock proteins), the continued synthesis of proteins involved in transcription and translation, and the repression of heat shock proteins. The addition of weak acid preservatives (for example, sorbates, benzoates) also induces a specific pattern of gene expression (for example, 'Acid Tolerance Response'), which is likely to be required for optimal adaptation of bacteria to weak acid preservatives and low pH. The primary mode of the antimicrobial action of low pH is to reduce the internal cell pH (pHi) below the normal physiological range tolerated by the cell, leading to growth inhibition. Survival mechanisms involve maintaining pH homeostasis, and this is achieved by a combination of passive and active mechanisms. Microorganisms adapt to osmotic stress by accumulating non-ionic or compatible solutes such as trehalose, glycerol, sucrose, and mannitol. These compatible solutes help balance the osmotic pressure and help preserve protein function inside the cells. By understanding and controlling such mechanisms of adaptation, it may be possible to prevent growth of key microorganisms in food products.2 COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY-Vol. 3, 2004 CRFSFS: Comprehensive Reviews in Food Science and Food Safety organisms will still be metabolically active and viable if transferred to favorable conditions (Busta 1978;Abbiss 1983;Ray 1986). Preservation techniques are designed to prevent microbial growth in processed foods, by disrupting the internal environment of the cell such that growth is no longer possible.Temperature, water activity, addition of preservatives, and pH are all parameters used to inhibit or destroy microorganisms and their spores and are also used as an aid for food preservation (Marechal and others 1999). Other parameters such as heat and bacteriostatic and bactericidal agents are also used in food preservation; they are not included in this review, but have been reviewed extensively (Lindquist 1986;Hendrick and Hartl 1993;Abee and Wouters 1999;Brul and Coote 1999). Some microorganisms have evolved and are capable of rapidly adapting to a continuously changing environment, thus developing tolerance or resistance to increased "doses" of particular stresses. Different types of organism possess different inherent resistances and susceptibilities to stress. For instance, Gram-negative bacteria are regarded as being more sensitive to cold shock, chilling, and freezing than Gram-positive bacteria (Straka ...

Transcriptome Analysis of Sorbic Acid-Stressed Bacillus subtilis Reveals a Nutrient Limitation Response and Indicates Plasma Membrane Remodeling

“…Sorbic acid (trans-trans-2,4-hexadienoic acid) is a six-carbon unsaturated fatty acid with a pK a of 4.76 and was first isolated from unripe berries of Rowan (Sorbus aucuparia). The acid, or its anionic salt, is used in a variety of food products and has a broad range of antimicrobial activities against spoilage bacteria, yeasts, and molds (5,17,57). However, the exact mechanism by which sorbate inhibits microbial growth is not entirely understood.…”

“…Depending on the species, bacteria can induce several systems to counteract a drop in the internal pH when encountering low pH stress. Among others, these include proton pumps, several decarboxylases (lysine, glutamate, and arginine), the production of urease, arginine deiminase, chaperones (e.g., DnaK and GroELS), and sigma factor (SigB, SigM, and RpoS)-mediated responses (5,6,14,31,67). However, the importance of low-pH stress response systems in weak-acid resistance development remains unclear.…”

nfluences of physicochemical stresses on injury and inactivation behaviour of Listeria innocua

“…As referred by Gabriel (2013) aside from some protection conferred by solutes against heat injury, the decrease in a w also brings forth physical damage to cellular membranes and provides reduction of intracellular moisture which can negatively affect the function of cellular enzymes. Exposures to IJFS October 2017 Volume 6 pages 139-151 acidic environments are also known to induce disruption of biochemical processes within the cells such as enzymes functions and nutrient transport (Beales, 2004). At higher temperatures, the study of Aljarallah and Adams (2007) showed that ribosomal inactivation was a primary target of cell damage.…”

Mutational Analysis of Transcriptional Initiation in Bacteria

“…An additional 19 promoters with changes in their -35 and -10 regions have been part of the Registry of Standard Biological Parts since 2004(MIT Working Group, 2005. The sequence of each mutant promoter is presented along with relative strengths determined by RFP expression data (http://parts.igem.org/Part:BBa_J23100).…”

“…For example, human brain cells need to express certain genes that are not needed in muscle cells, and vice versa (Gurdon & Melton, 2008). In a similar sense, bacteria must express different genes depending on temperature, pH, osmotic pressure, or the availability of food (Beales, 2004). Knowledge of gene regulation is important for understanding the differentiation and function of eukaryotic cells, the development of tissues in multicellular organisms, and the relationships of bacteria to their environments throughout the biosphere.…”