Abstract:
:The process by which an organism changes the composition of its membranal fatty acids in response to growth temperature, so as to maintain optimal membrane functioning, is known as homeoviscous adaptation (HA). One expression of HA is the constancy of the fluorescence polarization (P) of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in membranes of cells grown at various temperatures. The P of DPH in the membranes of Escherichia coli was shown by us to be inversely proportional to bacterial growth rate on different carbon sources. This result, implying failure of HA, is now complemented by measurements of DPH lifetimes, which indicate that the dominant variables contributing to the drop in P are (a) the order parameter of the membrane, which goes down, and (b) the fluidity, which may slightly increase. These are then the changes induced by enhanced growth rate. Two additional effects, cell membrane permeability and sensitivity to thermal shock, determined by the diffusion of o-nitrophenylgalactoside (ONPG) and by exposure to 52 degrees C, respectively, are reported to increase with growth rate. We can now conclude that there is a deviation from the principle of HA in E. coli grown at various rates, brought about by controlling the growth media at constant temperatures.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Parola AH,Ibdah M,Gill D,Zaritsky Adoi
10.1016/S0006-3495(90)82578-9subject
Has Abstractpub_date
1990-03-01 00:00:00pages
621-6issue
3eissn
0006-3495issn
1542-0086pii
S0006-3495(90)82578-9journal_volume
57pub_type
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