Lactobacillus plantarum has an unusually high Mn(II) requirement for growth and accumulated over 30 mM intracellular Mn(II). The acquisition of Mn(II) by L. plantarum occurred via a specific active transport system powered by the transmembrane proton gradient. The Mn(II) uptake system has a Km of 0.2 ,±M and a Vmax of 24 nmol mg-' of protein min-'. Above a medium Mn(II) concentration of 200 .,M, the intracellular Mn(II) level was independent of the medium Mn(II) and unresponsive to oxygen stresses but was reduced by phosphate limitation. At a pH of 5.5, citrate, isocitrate, and cis-aconitate effectively promoted MN(II) uptake, although measurable levels of 1,5-[ 4C]citrate were not accumulated. When cells were presented with equimolar Mn(II) and Cd(II), Cd(II) was preferentially taken up by the Mn(II) transport system. Both Mn(II) and Cd(II) uptake were greatly increased by Mn(II) starvation. Mn(II) uptake by Mn(II)-starved cells was subject to a negative feedback regulatory mechanism functiorting less than 1 min after exposure of the cells to Mn(II) and independent of protein synthesis. When presented with a relatively large amount of exogenous Mn(II), Mn(II)-starved cells exhibited a measurable efflux of their internal Mn(II), but the rate was only a small fraction of the maximal Mn(II) uptake rate. * Corresponding author. bacillaceae or Streptococcaceae. The, characteristics of the Mn(II) active transport system found in L. plantarum and reported here are consistent with efficient acquisition of Mn(II) from fermenting plant tissue or rumen habitats and shed more light on the unusual biochemistry of the lactic acid bacteria. MATERIALS AND M1:THODS L. plantarunM 14917 was obtained from the American Type Culture Collection, Rockville, Md. The lyophilized culture was grown, assessed for purity, and subcultured onto many small glucose-APT agar slants. After growth became visible, these slants were rapidly frozen and stored at-70°C. Each experiment employed a new frozen slant culture. Cells were grown on APT complex medium (2, 8) containing, per liter: tryptone, 10 g; yeast extract, 7.5 g; glucose, Na3citrate, 5 g; NaCl, 5 g; K2HPO4, 5 g; MgSO4, 0.8 g; Na2CO3, 1.25 g, MnSO4, 107 mg; and thiaminU-HCl, 0.1 mg. Tween 80 was omitted, the pH was adjusted to 6.7, and glucose and MnS04 were added after autoclaving. Omnission of MnSO4 produced low-Mn(II) APT containing 1.0 to i.8 puM Mn(II), derived from the tryptone and yeast extract. Broth cultures were grown in 40% filled Erlenmeyer flasks shaken at 116 rpm at 37°C. Culture growth wias followed turbidimetrically in sidearm flasks. Cells were counted under the microscope with a hemacytometer and related to the turbidimetric measurements. The APT salts bUiffer (pH 6.7) had the same composition as APT medium but lacked glucose, tryptone, yeast extract, Na3-citrate, thiamine-HCl, and MnSO4. Tranisport assays. Manganese uptake experiments were performed on Mn(II)-starved L. plantarum cells as follows. Cells from a 12 to 18-h APT agar plate culture were resuspended to an optic...

Among aerotolerant cells, Neisseria gonorrhoeae is very unusual because despite its obligately aerobic lifestyle and frequent isolation from purulent exudates containing polymorphonuclear leukocytes vigorously evolving O2- and H2O2, it contains no superoxide dismutase (SOD). Strains (14) of N. gonorrhoeae were compared with each other and with strains of Neisseria meningitidis, Neisseria mucosa, and Neisseria subflava under identical growth conditions for their contents of the oxy-protective enzymes catalase, peroxidase, and SOD, as well as respiratory chain proteins and activity. The absence of SOD from N. gonorrhoeae strains was demonstrated under a variety of oxygen-stress conditions. The neisserial species showed very different SOD, catalase, and peroxidase profiles. These profiles correlated well with the tolerance of the species to various intra- and extracellular oxygen insults. The high tolerance of N. gonorrhoeae for extracellular O2- and H2O2 appeared to be due to very high constitutive levels of peroxidase and catalase activity combined with a cell envelope impervious to O2-. Nevertheless, N. gonorrhoeae 19424 was much more sensitive to an intracellular flux of O2- than were the other (SOD-containing) neisserial species. The responses of N. gonorrhoeae and N. meningitidis respiratory and oxy-protective enzymes to growth under high and low oxygen tensions were followed, and a novel response, the apparent repression of the respiratory chain intermediates, respiration, and SOD, peroxidase, and catalase activity, was observed. The gonococcal catalase was partially purified and characterized. The results suggest that the very active terminal oxidase, low pO2 natural habitat, O2-stable catalase, and possibly the high glutathione content of the organism explain its aerobic survival in the absence of SOD.