Abstract

Rhodopseudomonas sphaerodes mutant H5 lacking 5-aminolevulinic acid synthase was grown phototrophically in chemostat cultures limited by malate. Tetrapyrrole formation was limited by 5-aminolevulinic acid. With variation of dilution rates the cultures exhibited two regions of almost constant cell protein, dry weight and bacteriochlorophyll levels suggesting the formation of two physiological modifications of the strain. These modifications were further characterized by differences in the rates of 5-aminolevulinic acid consumption, the production of reserve material, the stoichiometries of 5-aminolevulinic acid consumption and bacteriochlorophyll or cytochrome production, specific bacteriochlorophyll and cytochrome contents as well as the ratio of bacteriochlorophyll protein complexes. In contrast, cellular levels of coproporphyrin II stayed almost constant over the entire range of dilution rates employed. Bacteriochlorophyll and b-type cytochrome cellular levels exhibited hyperbolic dependencies on the specific rate of 5-aminolevulinic acid consumption, and c-type cytochrome levels a signmoidal dependency. Bacteriochlorophyll cellular levels showed a biphasic dependency with half maximal saturations at 2.6 and 15.4 nmol of 5-aminolevulinic acid consumed per mg of protein and h, and maximal levels of 15.2 and 21 nmol bacteriochlorophyll per mg of protein. Cellular levels of c- and b-type cytochromes were half maximally saturated at 19.5 and 14.5 nmol 5-aminolevulinic acid consumed per mg protein and h while maximal levels were reached at 0.5 and 0.17 nmol of c- and b-type cytochromes, respectively, per mg of protein.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.