Listeria innocua and Lactobacillus delbrueckii subsp. bulgaricus employ different strategies to cope with acid stress
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Responses of Listeria innocua and Lactobacillus delbrueckii subsp. bulgaricus to a rapid change in extracellular pH (pHex) from pHex 6 to a range of concentrations down to pHex 3.0 were examined, using HCl and lactic acid (LA) as acidulants. A new fluorescent probe 5-(and-6)-carboxy-2', 7'-dichlorofluorescein diacetate succinimidyl ester (CDCFDA-SE) was employed that enabled reliable measurements of intracellular pH (pHi) to a minimum pHi of 4.0. Changes in pHi and H+ fluxes from immobilised bacteria were measured using fluorescence ratio imaging microscopy (FRIM) and a non-invasive ion flux measuring technique (MIFE), respectively. L. innocua maintained a relatively constant pHi of 5.5-6.1 at pHex 4 and 5 via H+ extrusion. In contrast, L. delbrueckii subsp. bulgaricus progressively lowered pHi towards pHex over the entire pHex range examined. The type of acidulant used influenced pH regulation with both pHi and H+ -fluxes being more severely affected by LA compared to HCl. Overall, our data demonstrated different adaptive strategies in these two bacteria. While L. innocua expels protons to maintain a constant pHi, L. delbrueckii subsp. bulgaricus allows proton entry after acidic treatment so that pHi follows pHex.
Originalsprog | Engelsk |
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Tidsskrift | International Journal of Food Microbiology |
Vol/bind | 110 |
Udgave nummer | 1 |
Sider (fra-til) | 1-7 |
Antal sider | 7 |
ISSN | 0168-1605 |
DOI | |
Status | Udgivet - 2006 |
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