Syntrophism Among Prokaryotes

Abstract

The study of pure cultures in the laboratory has provided an amazingly diverse diorama of metabolic capacities among microorganisms, and has established the basis for our understanding of key transformation processes in nature. Pure culture studies are also prerequisites for research in microbial biochemistry and molecular biology. However, desire to understand how microorganisms act in natural systems requires the realization that microorganisms don’t usually occur as pure cultures out there, but that every single cell has to cooperate or compete with other microor macroorganisms. The pure culture is, with some exceptions such as certain microbes in direct cooperation with higher organisms, a laboratory artifact. Information gained from the study of pure cultures can be transferred only with great caution to an understanding of the behavior of microbes in natural communities. Rather, a detailed analysis of the abiotic and biotic life conditions at the microscale is needed for a correct assessment of the metabolic activities and requirements of a microbe in its natural habitat. In many cases, relationships of bacteria with other organisms may be relatively unimportant, as appears to be the case with most aerobes: they can usually degrade even fairly complex substrates to water and carbon dioxide without any significant cooperation with other organisms. Nutritional cooperation may exist, but may be re stricted to the transfer of minor growth factors, such as vitamins, from one organism to the other. However, we have to realize that this assumption is based on experience gained from pure cultures that were typically enriched and isolated in simple media, and the selection aimed at organisms