Resolving biogeochemical phenomena at high spatial resolution through electron microscopy

Abstract

Our understanding of microbe-metal interactions has advanced dramatically since the mid-1970s when little was known about the reactivity of bacterial cell wall components toward metal ions in the extracellular milieu. Although certain metals such as and Pb+ were known to react with components of bacterial cell walls and used to visualize their structure by electron microscopy (Garland et al., 1975), little physicochemical data were available on the specificity and sites of interactions (Humphrey & Vincent, 1966; Heptinstall et al., 1970; Irvin et al., 1975; Lambert et al., 1975; Raymond & MacLeod, 1975). Furthermore, there were no model systems to explorethe mechanisms of these interactions. This began to change when Beveridge and Murray used isolated cell walls of Bacillus subtilis to quantify metal ion binding to wall components. Beveridge demonstrated that cell walls concentrated cations such as Mg++, Na+, K+, Cu++ and Fe+++, but not Ba++, Li+ or Al+++ (Beveridge & Murray, 1976). Since these initial studies, Beveridge and his students and collaborators have contributed greatly to our understanding of the complex interactions between microbial cell surface polymers and metals in the environment. As fellow scientists working in this research area, we have developed a deep admiration of Beveridge’s scientific insight, technical skills and collegial demeanor. Not surprisingly, Beveridge’s research has had a significant impact on our research, as well as on the research of our collaborators and colleagues, and will likely influence the work of future generations of scientists working in the field of geobiology. Some examples are cited below.