Expression of colicin factor E2-P9

Hardy, K. G.; Harwood, Colin R.; Meynell, G. G.

doi:10.1007/bf00264862

Cited by 18 publications

(13 citation statements)

References 31 publications

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“…This increase in expression was shown not to be dependent on cell density or pH changes, two parameters which change when cells reach the stationary phase, but rather on starvation occurring when the growth medium is depleted of one or more nutrients. We also note that growth phase regulation has also been reported to control synthesis of colicin E2 (23). A 1,000-fold fluctuation in lacuna-forming cells (indicating colicin induction) was observed, depending on whether a pGE104 was carried in MC4100.…”

Section: Discussionsupporting

confidence: 52%

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Increased production of colicin E1 in stationary phase

Eraso¹,

Chidambaram²,

Weinstock³

1996

J Bacteriol

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The synthesis of colicin E1 is known to be regulated by the SOS response, anaerobiosis, and catabolite repression. The expression of cea-lacZ fusions was also found to be stimulated when cells reached stationary phase. This increase in expression was determined to be due to depletion of nutrients from the medium, since the addition of fresh medium reversed the effect. Expression of the fusion increased when cells were starved in 10 mM MgSO 4 and when they were grown in conditioned medium in which cells had been grown previously. The stimulation of expression occurred when the cea-lacZ fusion was present in single-copy as well as in multicopy plasmids. Finally, the data were consistent with this increase being independent of the SOS response, anaerobiosis, catabolite repression, and integration host factor as well as the stationary-phase regulators encoded by rpoS and lrp.

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Section: Discussionsupporting

confidence: 52%

“…cells were in the exponential or stationary phase of growth (23). Thus, this type of regulation could be general for all colicins.…”

Section: Discussionmentioning

confidence: 91%

Increased production of colicin E1 in stationary phase

Eraso¹,

Chidambaram²,

Weinstock³

1996

J Bacteriol

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“…In natural environments, analogous cells could continue to be involved in important biotransformations irrespective of whether they were ever able to replicate. More significantly, in the case of the two pathogens studied here, such putatively active but non-viable cells could remain in host tissues where, like certain colicin-producing cells (Hardy et aL, 1974), they might produce toxins or express other virulence factors well after they had ceased to be detectable by conventional culture methods.…”

Section: Discussionmentioning

confidence: 99%

Detection of induced β‐galactosidase activity in individual non‐culturable cells of pathogenic bacteria by quantitative cytological assay

Nwoguh

Harwood

Barer³

1995

Molecular Microbiology

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One Escherichia coli and two F' lac+ Salmonella strains were carbon and nitrogen stressed at 37 degrees C over 35 days in the presence or absence of chloramphenicol; the number, activity and culturability of cells in the resultant populations were studied. Active cells were enumerated by fluorescence microscopy after treatment with the lac inducer IPTG and cytological assay for beta-galactosidase. In all experiments, active and total cell counts remained within a three-fold range of each other and their initial values, while culturability fell by > 10(8)-fold and 10(3)-fold in chloramphenicol-treated and untreated preparations, respectively. Quantitative image analysis revealed different distributions of cell-specific fluorescence and indicated a progressive decline in the levels of induced enzyme activity in both E. coli and Salmonella enteritidis. It was concluded that the non-culturable cells studied retained inducible enzyme activity and that this activity did not result from a starvation-induced programme of gene expression. Whether or not such active but non-culturable cells are viable, they are clearly responsive and have the potential to influence their environment. The assay described can be applied to heterogeneous populations and environments and shows considerable potential for the study of gene expression at the single cell level.

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“…The percentage of lacuna-forming cells (%LFC) in ColE2-P9+ broth cultures varies considerably depending on the growth phase (230,232). The %LFC remains at a constant minimum value of about 0.01% in exponentially growing broth cultures which have a colony count of less than 5 x 107/ml.…”

Section: Colicins Relationships Between Colicinsmentioning

confidence: 99%

“…0.01%. Cells releasing colicin exist for several hours but they do not divide to produce lacunaforming daughter cells (230). Spontaneous induction of prophages varies similarly in batch cultures (381).…”

Section: Colicins Relationships Between Colicinsmentioning

confidence: 99%