Tolerance to acid in pH 5.0-grown organisms of potentially pathogenic Gram-negative bacteria

Nojoumi, Seyed Ali; Smith, David George Emslie; Rowbury, R. J.

doi:10.1111/j.1472-765x.1995.tb01081.x

Cited by 15 publications

(13 citation statements)

References 7 publications

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“…For bacteria to thrive inside these microhabitats, they must survive digestion and the acidic condition. The observed lowest pH (5.40) in our study is well within the tolerable range for most bacteria (Cotter and Hill 2003;Nojoumi et al 2008), including anaerobes (Lowe et al 1993), and diverse, viable bacterial communities have been recovered from copepod guts (Delille and Razouls 1994;Hansen and Bech 1996). On the other hand, the organic-rich environment inside a copepod gut may even support higher bacterial growth than the ambient ocean (Tang 2005).…”

Section: Discussionmentioning

confidence: 71%

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Tang¹,

Glud²,

Glud³

et al. 2011

Limnology & Oceanography

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The environmental conditions inside the gut of Calanus hyperboreus and C. glacialis were measured with microelectrodes. An acidic potential hydrogen (pH) gradient was present in the gut of C. hyperboreus, and the lowest pH recorded was 5.40. The gut pH of a starved copepod decreased by 0.53 after the copepod resumed feeding for a few hours, indicating the secretion of acidic digestive fluid. A copepod feeding on Thalassiosira weissflogii (diatom) had slightly lower pH than that feeding on Rhodomonas salina (cryptophyte). Oxygen was undersaturated in the gut of both C. hyperboreus and C. glacialis, with a steep gradient from the anal opening to the metasome region. The central metasome region was completely anoxic. Food remains in the gut led to a lower oxygen level, and a diatom diet induced a stronger oxygen gradient than a cryptophyte diet. The acidic and suboxic-anoxic environments of the copepod gut may support iron dissolution and anaerobic microbial activities that otherwise are not favored in the well-buffered and oxygenated ambient ocean.

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Section: Discussionmentioning

confidence: 71%

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Tang¹,

Glud²,

Glud³

et al. 2011

Limnology & Oceanography

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“…A gradual increase in acidity can allow induced tolerance to acid to occur (acid habituation), and this will permit the organisms to survive subsequent exposures which could be lethal to nonhabituated cells (2,20,21,27). The effect of such an adaptive response on the permeability properties of gramnegative bacteria should be examined, especially with enteric pathogens such as E. coli O157:H7.…”

Section: Discussionmentioning

confidence: 99%

Lactic Acid Permeabilizes Gram-Negative Bacteria by Disrupting the Outer Membrane

Alakomi

Skyttä

Saarela

et al. 2000

Appl Environ Microbiol

790

504

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The effect of lactic acid on the outer membrane permeability of Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium was studied utilizing a fluorescent-probe uptake assay and sensitization to bacteriolysis. For control purposes, similar assays were performed with EDTA (a permeabilizer acting by chelation) and with hydrochloric acid, the latter at pH values corresponding to those yielded by lactic acid, and also in the presence of KCN. Already 5 mM (pH 4.0) lactic acid caused prominent permeabilization in each species, the effect in the fluorescence assay being stronger than that of EDTA or HCl. Similar results were obtained in the presence of KCN, except for P. aeruginosa, for which an increase in the effect of HCl was observed in the presence of KCN. The permeabilization by lactic and hydrochloric acid was partly abolished by MgCl 2 . Lactic acid sensitized E. coli and serovar Typhimurium to the lytic action of sodium dodecyl sulfate (SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosa was effectively sensitized to lysozyme by lactic acid and by HCl. Considerable proportions of lipopolysaccharide were liberated from serovar Typhimurium by these acids; analysis of liberated material by electrophoresis and by fatty acid analysis showed that lactic acid was more active than EDTA or HCl in liberating lipopolysaccharide from the outer membrane. Thus, lactic acid, in addition to its antimicrobial property due to the lowering of the pH, also functions as a permeabilizer of the gram-negative bacterial outer membrane and may act as a potentiator of the effects of other antimicrobial substances.Lactic acid, as produced by lactic acid starter culture bacteria or as an additive to foods, functions as a natural antimicrobial having a generally recognized as safe status. As reviewed by Doores (8), lactic acid is able to inhibit the growth of many types of food spoilage bacteria, including gram-negative species of the families Enterobacteriaceae and Pseudomonadaceae. Among other organic acids, lactic acid is recognized as a biopreservative in naturally fermented products (25), and numerous applications for decontamination of meat by lactic acid have been described (7,10,22,29,32,33). The antibacterial action of lactic acid is largely, but not totally, assigned to its ability in the undissociated form to penetrate the cytoplasmic membrane, resulting in reduced intracellular pH and disruption of the transmembrane proton motive force (25).The relative efficacy of lactic acid against gram-negative bacteria is not unexpected considering that as a small watersoluble molecule lactic acid gains access to the periplasm through the water-filled porin proteins of the outer membrane (OM), as reviewed by Nikaido (18). The OM, however, functions as an efficient permeability barrier that is able to exclude macromolecules (such as bacteriocins or enzymes) and hydrophobic substances (i.e., hydrophobic antibiotics). The permeability ...

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“…Raw meat and poultry are usually considered ideal growth media for bacteria; however, all microbial contaminants are subjected to physical, chemical, and nutritional stresses during processing (Yousef and Courtney, 2003). Bacteria can face exposure to extremes of acidity in many situations in the environment, in foods, and in the bodies of animals or humans (Nojoumi et al, 1995). The USDA supports use of a mixture of pathogenic bacterial strains containing relatively heat-resistant serovars, particularly those that have been implicated in outbreaks, to verify compliance with performance standards (USDA/FSIS, 2001).…”

Section: Introduction S Ince Its First Recognition As a Foodbornementioning

confidence: 99%

Thermal Tolerance of Acid-Adapted and Non-adaptedEscherichia coliO157:H7 andSalmonellain Ground Beef During Storage

Singh

Simpson²,

Mullins³

et al. 2006

Foodborne Pathogens and Disease

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Thermal tolerance of acid-adapted Escherichia coli O157:H7 or Salmonella in ground beef was evaluated during storage at 4 degrees C or -20 degrees C. Both pathogens were adapted to acidic conditions (pH approximately 4.6) by growing in tryptic soy broth supplemented with 1% glucose. A five-strain cocktail of E. coli O157:H7 or Salmonella was grown separately in TSB (pH approximately 6.6) and TSB + 1% glucose for 24 h at 37 degrees C to provide cells with or without acid adaptation. Irradiated ground beef was inoculated with either acid-adapted or non-adapted E. coli O157:H7 or Salmonella; the samples stored at 4 degrees C were subjected to heat treatment at 62 degrees C or 65 degrees C on days 1, 7, 14, 21, and 28, and the samples stored at -20 degrees C were subjected to heat treatment at 62 degrees C or 65 degrees C on days 1, 30, 60, 90, and 120. Decimal reduction time (D values) of the pathogens was determined as an indicator of thermal tolerance. Significantly higher D(62) values were observed on days 21 and 28 for non-adapted E. coli O157:H7 stored at 4 degrees C and on days 90 and 120 for non-adapted E. coli O157:H7 stored at -20 degrees C (P < 0.05). Higher D(62) values were observed on days 21 and 28 among non-adapted Salmonella strains stored at 4 degrees C and on day 28 for acid-adapted strains of Salmonella stored at 4 degrees C (P < 0.05). Higher D(62) values for acid-adapted strains of Salmonella stored at -20 degrees C were observed on days 30, 60, and 90 (P < 0.05), when while no differences were observed in the D(65) values of acid-adapted and non-adapted strains of E. coli O157:H7 and Salmonella throughout storage at both temperatures (P > 0.05). This suggests that acid adaptation of foodborne pathogens provides a certain level of protection against heat treatment at lower cooking temperatures, while at higher temperatures there were no observed differences between the sensitivity of acid-adapted and non-adapted strains in an actual food system over an extended period of refrigerated and frozen storage.

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Tolerance to acid in pH 5.0-grown organisms of potentially pathogenic Gram-negative bacteria

Cited by 15 publications

References 7 publications

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Copepod guts as biogeochemical hotspots in the sea: Evidence from microelectrode profiling of Calanus spp

Lactic Acid Permeabilizes Gram-Negative Bacteria by Disrupting the Outer Membrane

Thermal Tolerance of Acid-Adapted and Non-adaptedEscherichia coliO157:H7 andSalmonellain Ground Beef During Storage

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