Low temperature inhibition on binding, transport, and incorporation of leucine, arginine, methionine, and histidine in Escherichia coli

Abstract

A multiple amino acid auxotroph and a wild type of Escherichia colk K12 were used to study the effects of near minimum growth temperatures on the binding, transport, and cellular incorporation of selected amino acids. Both strains of the bacterium showed the same minimum growth temperature (8 "C) when previously grown at 15 "C. At 8 "C and above, the auxotroph exhibited an overall greater ability to bind and transport amino acids than did the wild type. Below the minimum growth temperature, transport and cellular incorporation including respiration (uptake) were significantly lower for either organism. The NEU and HEPPEL osmotic shock treatment indicated the removal of the specific histidine-binding protein and the ability to bind histidine was not recovered by further incubation below 8 O C . A t 8 "C and above, the cells recovered their ability to bind histidine within one hour. The evidence presented indicates a direct relationship between the auxotroph's minimum growth temperature and its ability to bind amino acids, specifically methionine.The temperature range of growth for microorganisms extends from below 0 "C to greater than 80 "C. Any one species, however, can generally grow only over a maximum range of 40 "C and some psychrophiles, having a maximum growth temperature below 20 "C, may have a considerably narrower temperature range of growth. The determining biochemical or physical factor(s) which limit the growth of all microorganisms to a specific minimum and maximum temperature are not understood.I n contrast t o some thermophiles, neither macromolecular synthesis nor fatty acid composition are involved in limiting the temperature range of growth of Escherichia coli (SHAW and INaRAHAM 1965, 1967). However, DAS and GOLDSTEIN (1968) suggested that the minimum growth temperature for E . coli may involve the inability of ribosomal subunits to bind mRNA a t temperatures below the minimum. For Candida l i plytica, BAXTER and GIBBONS (1962) suggested that the transport of substrate into the yeast is temperature-dependent. The inability to transport substrate a t the organism's minimum growth temperature could be the basis for cessation of growth.This investigation deals with the transport of labelled (I4C) amino acids into E . coli below, at, and above the organism's minimum growth temperature t o help elucidate the physiological basis for the minimum growth temperature. Materials and methodsBacterial strains and cell preparation: Escherichia coli K12 strains UC175, a wild type, and UC41(leu2, lacl, gal, hid, aryG-6, met, mal, xyl. strr, Ar), an auxotroph, were obtained from Dr. LYLE BROWN, Department of Microbiology, Oregon State University, Corvallis, Oregon. The strains were maintained on nutrient agar (DIFCO) slants. For experimental purposes, the cells were grown in nutrient broth (DIFCO) a t 15 "C on a reciprocating shaker. The cells were harvested by centri-

The microbial food web in Arctic seawater concentration of dissolved free amino acids and bacterial abundance and activity in the Arctic Ocean and in Resolute Passage

“…This temporal distribution of primary production, and the limited microbial response to the bloom of ice algae, may have a favorable effect on secondary production in the Canadian archipelago. These observations, as well as those of Smith et al (1989) and Pomeroy & Deibel (1986), and earlier experimental work by Goodrich & Morita (1977) and Christian & Wiebe (1974) suggest that bacterial assimilation of substrates in cold water may be limited by an interaction of temperature and substrate concentration. Haight & Morita (1966) found that membrane permeation and glycolytic enzyme level of Vibrio marinus MP-l were impaired when cultured at 4 "C with unamended seawater as the growth medium.…”

“…4). It is interesting to compare our estimates of turnover time for leucine (Table 4) Because of the lower specific activity of the 14C-glutamic acid, as compared with the 3H-leucine, we were increasing the glutamic acid concentration significantly and therefore we were really performing an enrichment experiment, as have others who have used '4C-glutamic acid in this way (Morita et al 1977). The result may be a higher rate of uptake than occurs at the vanishingly low glutamic acid concentratlons that were present, both in the Arctic Ocean and Resolute Passage.…”

Survival, physiological response and recovery of enteric bacteria exposed to a polar marine environment

“…After 15 days of exposure, plate counts on TLYD and TLY decreased steadily, with Tg9 values of 360 and 504 h, respectively. As with E. coli and S. typhimurium, injury reached its highest initial value of 80% at 4 days and then increased to 99% because of a sharp 2-log-unit decrease in TLYD counts by 15 days, while TLY counts remained stable (Fig. 2).…”

“…12°C (9, 28). Previous short-term cold exposure experiments have also shown that translation initiation, as well as binding and transport of amino acids, is inhibited in E. coli below 8°C (7,15). However, transport, incorporation, and mineralization of added amino acids were not completely inhibited.…”