Under optimal growth conditions in SYPHC medium the generation time of

strain Ivo14T was 13 h and thus quite long compared to the related type AMN-107 molecular weight strains of Chromatocurvus halotolerans, C. litoralis and H. rubra, which have mean doubling times of 8.7, 4.5 and 3.4 h, respectively. As a peculiarity the requirements of Ivo14T for growth in defined medium were more complex than that of C. litoralis, H. rubra or Chromatocurvus halotolerans. In respect to mineral composition Ivo14T required in addition to sodium chloride, magnesium and calcium ions, whereas C. litoralis required besides NaCl only either Mg2+ or Ca2+. In addition, there seems to be a requirement for certain amino acids. In defined media L-histidine was found to be an essential nutrient for growth of Ivo14T. No growth was detected below 40 μmol/l L-histidine in the medium. The growth-stimulating effect was not check details concentration P505-15 supplier dependent within the tested range of up to 500 μmol/l. It was also found that L-histidine could be replaced with either L-threonine or L-aspartate, which have completely different pathways of biosynthesis. Interestingly, all three amino acids are common substrates for enzymatic phosphorylation reactions. Consequently, this rather indicates a defect in the global regulation of amino

acid synthesis, e.g. the stringent response [33, 34], than an auxotrophy for certain amino acids. In subsequent experiments a combination of L-histidine and L-cysteine, each in a concentration of 250 μM, was shown to be optimal for growth and expression of photosynthetic pigments in strain Ivo14T. L-histidine stimulated also the growth of H. rubra in defined media by shortening the observed lag-phase, but it was not an essential compound for growth. There was no difference in the requirement of vitamins among the four related Methane monooxygenase BChl

a-containing strains, which all needed biotin, thiamine and B-12. However, some variation in the sensitivity to antibiotics was found. In contrast to C. litoralis, strain Ivo14T was resistant to cefalotin, but sensitive to bacitracin and doxycycline. H. rubra and Chromatocurvus halotolerans could be distinguished from the former two strains by their resistance to imipenem. H. rubra was clearly distinct to all strains, because it was only sensitive to chloramphenicol, bacitracin and gentamicin in the applied disk diffusion test encompassing a total of 13 different antibiotics. Substrate utilization pattern and enzyme activities The utilization of carbon sources and enzyme activities were determined for the novel strain Ivo14T and type strains of the related pigmented species Chromatocurvus halotolerans and H. rubra. The three strains of BChl a-containing aerobic gammaproteobacteria analyzed in this study and C.