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Expression of Cholera Toxin by El Tor Vibrio cholerae in Shallow Culture Growth Conditions

Författare och institution:
Mayra Cobaxin (-); Haydee Martinez (-); Guadalupe Ayala (-); Jan Holmgren (Institutionen för biomedicin, avdelningen för mikrobiologi och immunologi); Åsa Sjöling (Institutionen för biomedicin, avdelningen för mikrobiologi och immunologi); Joaquin Sanchez (-)
Publicerad i:
Microbial Pathogenesis, 66 s. 5-13
Artikel, refereegranskad vetenskaplig
Sammanfattning (abstract):
Vibrio cholerae O1 classical, El Tor and O139 are the primary biotypes that cause epidemic cholera, and they also express cholera toxin (CT). Although classical V. cholerae produces CT in various settings, the El Tor and O139 strains require specific growth conditions for CT induction, such as the so-called AKI conditions, which consist of growth in static conditions followed by growth under aerobic shaking conditions. However, our group has demonstrated that CT production may also take place in shallow static cultures. How these type of cultures induce CT production has been unclear, but we now report that in shallow culture growth conditions, there is virtual depletion of dissolved oxygen after 2.5 h of growth. Concurrently, during the first three to 4 h, endogenous CO2 accumulates in the media and the pH decreases. These findings may explain CT expression at the molecular level because CT production relies on a regulatory cascade, in which the key regulator AphB may be activated by anaerobiosis and by low pH. AphB activation stimulates TcpP synthesis, which induces ToxT production, and ToxT directly stimulates ctxAB expression, which encodes CT. Importantly, ToxT activity is enhanced by bicarbonate. Therefore, we suggest that in shallow cultures, AphB is activated by initial decreases in oxygen and pH, and subsequently, ToxT is activated by intracellular bicarbonate that has been generated from endogenous CO2. This working model would explain CT production in shallow cultures and, possibly, also in other growth conditions.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Medicinska grundvetenskaper ->
Mikrobiologi inom det medicinska området
Vibrio choleare; Model for cholera toxin expression; El Tor vibrios; Endogenous bicarbonate; ToxT regulator; Low oxygen and AphB regulation; Shallow cultures
Postens nummer:
Posten skapad:
2014-01-07 12:06
Posten ändrad:
2014-01-29 10:05

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