A MICROBIOLOGISTS ODYSSEY - BACTERIAL-VIRUSES TO PHOTOSYNTHETIC BACTERIA

Perspective can be defined as the relationships of relative importance of facts or matters from any special point of view. Thus, my Personal perspective reflects the threads I followed in a 50-year journey of r esearch in the complex tapestry of bioenergetics and various aspects o f microbial metabolism. An early interest in biochemical and microbial evolution led to the fertile hunting grounds of anoxygenic photosynth etic bacteria. Viewed as a physiological class,these organisms show re markable metabolic versatility in that certain individual species are capable of using all the known major types of energy conversion (photo synthetic, respiratory, and fermentative) to support growth. since suc h anoxyphototrophs are readily amenable to molecular genetic/biologica l manipulation, it can be expected that they will eventually provide i mportant clues for unraveling the evolutionary relationships of the se veral kinds of energy conversion. I gradually came to believe that und erstanding the evolution of phototrophs would require detailed knowled ge not only of how light is converted to chemical energy, but also of a) pathways of monomer production from extracellular sources of carbon and nitrogen and b) mechanisms cells use for integrating ATP regenera tion withthe energy-requiring biosyntheses of biological macromolecule s. Serendipic observation of photoproduction of H2 from organic compou nds by Rhodospirillum rubrum in 1949 led to discovery of N2 fixation b y anoxyphototrophs, and this capacity was later exploited for the isol ation of hitherto unknown species of photosynthetic prokaryotes, inclu ding the heliobacteria. Recent studies on the reaction centers of the heliobacteria suggest the possibility that these bacteria are descende nts of early phototrophs that gave rise to oxygenic photosynthetic org anisms.