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phototrophic picoplankters. In the prokaryotic world, however, few other microbes can be so
readily identified and quantified. More typically, few distinguishing morphological criteria are
available to differentiate diverse microbial species found in environmental samples. Most
bacteria are therefore characterized on the basis of biochemical and physiological properties
determined on pure cultures. Unfortunately, not all microbes are amenable to cultivation, and
so they are difficult to identify, differentiate, and characterize. Molecular biological techniques
may offer a means to resolve some of these difficulties and so facilitate the identification and
quantitation of individual microbial species in mixed populations. In particular, the use of
macromolecular sequence data for systematic, evolutionary and ecological studies has
significant potential.
Why study individual bacteria and bacterial species? It is now well accepted that
microorganisms playa major role in the biogeochemical cycling of organic and inorganic
material in the marine environment. This view stems from the currently recognized high
abundance of bacteria, cyanobacteria, and microeukaryotes in seawater (Hobbie et al., 1977;
Waterbury et al., 1979; Ducklow, 1983; Fenchel, 1982), and the observation that planktonic
bacteria are metabolically quite active (Fuhrman and Azam, 1982; Hagstrom et al., 1979;
Karl, 1986). Although the general details of marine bacterial abundance are fairly well
characterized, many ecologically important aspects of marine microbial population structure
and dynamics are virtually unstudied. There is very little information concerning the complex
interactions of different physiological types of marine bacteria, which exist as synergistic
microbial consortia in the oceanic environment (Sieburth, 1988). Little is known about the
actual species composition of marine bacterial populations, because typically less than a few
percent of directly enumerated marine bacteria can be isolated and studied by standard
cultivation techniques (Jannasch and Jones, 1959; Ferguson et al., 1984). Variability in the
types of marine bacteria which occupy different niches, such as bacteria attached to
particulates versus free-living bacterioplankton, also remains largely unstudied. Knowledge
of this variability would greatly facilitate correlations of bacterial population structure to the
bacterial processes which mediate the flow of energy and matter in the sea.
phototrophic picoplankters. In the prokaryotic world, however, few other microbes can be so
readily identified and quantified. More typically, few distinguishing morphological criteria are
available to differentiate diverse microbial species found in environmental samples. Most
bacteria are therefore characterized on the basis of biochemical and physiological properties
determined on pure cultures. Unfortunately, not all microbes are amenable to cultivation, and
so they are difficult to identify, differentiate, and characterize. Molecular biological techniques
may offer a means to resolve some of these difficulties and so facilitate the identification and
quantitation of individual microbial species in mixed populations. In particular, the use of
macromolecular sequence data for systematic, evolutionary and ecological studies has
significant potential.
Why study individual bacteria and bacterial species? It is now well accepted that
microorganisms playa major role in the biogeochemical cycling of organic and inorganic
material in the marine environment. This view stems from the currently recognized high
abundance of bacteria, cyanobacteria, and microeukaryotes in seawater (Hobbie et al., 1977;
Waterbury et al., 1979; Ducklow, 1983; Fenchel, 1982), and the observation that planktonic
bacteria are metabolically quite active (Fuhrman and Azam, 1982; Hagstrom et al., 1979;
Karl, 1986). Although the general details of marine bacterial abundance are fairly well
characterized, many ecologically important aspects of marine microbial population structure
and dynamics are virtually unstudied. There is very little information concerning the complex
interactions of different physiological types of marine bacteria, which exist as synergistic
microbial consortia in the oceanic environment (Sieburth, 1988). Little is known about the
actual species composition of marine bacterial populations, because typically less than a few
percent of directly enumerated marine bacteria can be isolated and studied by standard
cultivation techniques (Jannasch and Jones, 1959; Ferguson et al., 1984). Variability in the
types of marine bacteria which occupy different niches, such as bacteria attached to
particulates versus free-living bacterioplankton, also remains largely unstudied. Knowledge
of this variability would greatly facilitate correlations of bacterial population structure to the
bacterial processes which mediate the flow of energy and matter in the sea.