This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Phoenix, V. R. Articles by Ferris, F. G. Search for Related Content PubMed PubMed Citation Articles by Phoenix, V. R. Articles by Ferris, F. G. Agricola Articles by Phoenix, V. R. Articles by Ferris, F. G.

Characterization and Implications of the Cell Surface Reactivity of Calothrix sp. Strain KC97

Department of Geology, University of Toronto, Toronto, Ontario M5S 3B1, Canada,¹ School of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom²

Received 25 March 2002/ Accepted 11 July 2002

The cell surface reactivity of the cyanobacterium Calothrix sp. strain KC97, an isolate from the Krisuvik hot spring, Iceland, was investigated in terms of its proton binding behavior and charge characteristics by using acid-base titrations, electrophoretic mobility analysis, and transmission electron microscopy. Analysis of titration data with the linear programming optimization method showed that intact filaments were dominated by surface proton binding sites inferred to be carboxyl groups (acid dissociation constants [pK_a] between 5.0 and 6.2) and amine groups (mean pK_a of 8.9). Sheath material isolated by using lysozyme and sodium dodecyl sulfate generated pK_a spectra similarly dominated by carboxyls (pK_a of 4.6 to 6.1) and amines (pK_a of 8.1 to 9.2). In both intact filaments and isolated sheath material, the lower ligand concentrations at mid-pK_a values were ascribed to phosphoryl groups. Whole filaments and isolated sheath material displayed total reactive-site densities of 80.3 x 10^-5 and 12.3 x 10^-5 mol/g (dry mass) of cyanobacteria, respectively, implying that much of the surface reactivity of this microorganism is located on the cell wall and not the sheath. This is corroborated by electrophoretic mobility measurements that showed that the sheath has a net neutral charge at mid-pHs. In contrast, unsheathed cells exhibited a stronger negative-charge characteristic. Additionally, transmission electron microscopy analysis of ultrathin sections stained with heavy metals further demonstrated that most of the reactive binding sites are located upon the cell wall. Thus, the cell surface reactivity of Calothrix sp. strain KC97 can be described as a dual layer composed of a highly reactive cell wall enclosed within a poorly reactive sheath.

This article has been cited by other articles:

• Micheletti, E., Pereira, S., Mannelli, F., Moradas-Ferreira, P., Tamagnini, P., De Philippis, R. (2008). Sheathless Mutant of Cyanobacterium Gloeothece sp. Strain PCC 6909 with Increased Capacity To Remove Copper Ions from Aqueous Solutions. Appl. Environ. Microbiol. 74: 2797-2804 [Abstract] [Full Text]  
• Douglas, S. (2005). Mineralogical footprints of microbial life. ajs 305: 503-525 [Abstract] [Full Text]  
• Borrok, D., Turner, B. F., Fein, J. B. (2005). A universal surface complexation framework for modeling proton binding onto bacterial surfaces in geologic settings. ajs 305: 826-853 [Abstract] [Full Text]  
• Martinez, R. E., Ferris, F. G. (2005). Review of the surface chemical heterogeneity of bacteriogenic iron oxides: Proton and cadmium sorption. ajs 305: 854-871 [Abstract] [Full Text]