Microbial Cultures and Natural Populations

Abstract

For some years there have been descriptions, particularly from oligotrophy environments, of microorganisms that evade culture. Initially these were based upon the very low proportion of colonies obtained relative to the number of microscopically observed bacteria in a sample. Recently there has been several papers that, using molecular biological methods, describe a much greater phylogenetic diversity of bacteria in the open ocean than could have been forecast from traditional means of bacterial culture (see Giovannoni, 1995). Without doubt this is partly a result of our less than perfect skills in isolation but the very low recovery rate reported, often 1 in 10³ or 10⁴ leads one to think that other factors may be involved. When bacteria are brought into culture and maintained in the laboratory their growth rate and maximum culture density often increase over periods of months or even years. They ‘adapt’ to laboratory culture. The roots of the idea that the organisms that microbiologists study in the laboratory are often but not always only representative, rather than a cross section, of those from their natural environment is not new and goes back to what has been termed the golden age of bacteriology around the end of the nineteenth century.