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.