Volume of extracellular polymeric substance coverage of individual Acidithiobacillus ferrooxidans bacterium measured by atomic force microscopy

Abstract

The Acidithiobacillus ferrooxidans response to stress associated with the drying process is known to be the production of extracellular polymeric substance (EPS) coverage. Here, samples of A. ferrooxidans suspensions grown in 1.8 pH and 3.0 pH and dried on mica and silicon are shown to form a structure of isolated bacteria. Individual bacteria coverage patterns were imaged by atomic force microscopy (AFM) on hydrophobic (silicon) and hydrophilic (mica) substrates. A comparison of images of covered and uncovered bacteria establish the volume of individual EPS coverage. The EPS production for bacteria on hydrophobic substrates shows a substantial decrease (a factor of 30) in the EPS volume per bacterium when compared with the one on hydrophilic substrates. Shape and volume determination of EPS structures on bacteria as a function of hydrophobicity or hydrophilicity of the substrate may help to determine the functions of EPS on bacterial aggregates.

Are the Soft, Liquid-Like Structures Detected around Bacteria by Ambient Dynamic Atomic Force Microscopy Capsules?

“…It was usually necessary to repetitively image the same area until a noise-free image could be obtained. Teschke reported that images could be not obtained in some of the areas explored in an evaporated bacterial spot due to their highly viscoelastic properties (33). This is compatible with our experience, and it is possible that they were moving on areas extensively covered by soft liquid-like substances that made their imaging so unstable.…”

Quorum sensing detected by atomic force microscopy imaging of corrals surrounding multicellular arrangement of bacteria

“…The bacterial suspension was deposited on a substrate and the total amount of sugar was determined. According to the results shown in Figure 7 the amount of sugar increased after a period of 24 h. Moreover, EPS produced by bacteria hold several times their weight in water (Roberson and Firestone, 1992;Teschke, 2005). Hence, the EPS form a highly entangled hydrated structure composed basically of sugars and hydrogen-bonded water; this is in perfect agreement with our optical observations, suggesting that the EPS covering behaves as an isotropic gel-like structure.…”

“…During imaging, the contact force was kept below 1 nN and the scan rate in the range of 1-4 Hz. Details about our experimental setup have been published elsewhere (Sassaki et al, 1996;Teschke, 2005).…”

“…In particular, AFM has recently proved to be useful in imaging morphology of bacteria (da Silva and Teschke, 2003), liposomes (Teschke, 2002), and DNA molecules (Teschke et al, 1997) on solid surfaces. Recently, we reported that AFM imaging could be used to determine the volume of EPS covering individual cells (Saa and Teschke, 2006;Teschke, 2005).…”

“…Structures formed by extracellular polymeric substances covering individual Acidithiobacillus ferrooxidans (A. ferrooxidans) bacteria on hydrophilic mica plates were preliminarily analyzed by means of atomic force microscopy (AFM) imaging (Teschke, 2005). This report uses the term glycocalyx to refer to the layer of exopolysaccharides (EPS) matrix surrounding the microbial cells.…”