Mikrobiol. Z. 2015; 77(3):9-15. Russian.
doi: https://doi.org/10.15407/microbiolj77.03.009

Wet-mode Scanning Electron Microscopy as an Instrument for Studies
of Biogeochemical Processes of Fungal Biominerals Formation

Fomina M.A., Podgorsky V.S.

Zabolotny Institute of Microbiology and Virology, NAS of Ukraine
154 Akad. Zabolotny Str., Kyiv, 03143, Ukraine

The aim of this work was to examine the potential of the use of one of the modem approaches in scanning electron microscopy - the wet mode ESEM to study biogeochemical processes of biominerals formation by micromycetes. The object of the study was microscopic fungus Beauveria caledonica known for its ability to transform metals and minerals. In response to the presence of copper phosphate in the medium, it was observed the abundant formation of copper oxalate crystals in fungal mycelium. Optimal visualization at wet mode was achieved at the sample chamber pressure around 6 torr and relative humidity 85 - 90 %. The comparison of the observations obtained using high-vacuum mode and wet mode scanning electron microscopy showed that in their natural state fungal hyphae and mycelial cords are surrounded by thick hydrated mucilaginous sheath which serves as a matrix for biogeochemical processes of secondary minerals formation and growth. The wet mode and high-vacuum mode scanning electron microscopies complement each other in comprehensive study of biogeochemical role of microscopic fungi in transformations of metals and minerals.

Key words: scanning electron microscopy, ESEM, microscopic fungi, biogeochemistry, biominerals, Beauveria caledonica.

Full text (PDF, in Russian)

  1. Burford E.P., Fomina M., Gadd G.M. Fungal involvement in bioweathering and biotransforma­ tion of rocks and minerals. Mineral. Mag. 2003; 67(6):1127-1155. https://doi.org/10.1180/0026461036760154
  2. Connolly J.H., Jellison J. Calcium translocation, calcium oxalate accumulation, and hyphal sheath morphology in the white rot fungus Resinicium bicolour. Can. J. Bot. 1995; 73(6):927-936. https://doi.org/10.1139/b95-101
  3. Danilatos G.D. Foundations of environmental scanning electron microscope. Adv. Elect. Electron. Phy. V.71. San-Diego: Academic Press, 1988. P. 109-250.
  4. Douglas S., Douglas D.D. Environmental scanning electron microscopy studies of colloidal sulphur deposition in a natural microbial community from a cold sulfide spring near Ancaster, Ontario, Canada. Geomicrobiol. J. 2000; 17(4):275-289. https://doi.org/10.1080/01490450050192974
  5. Fomina M., Hillier S., Charnock J.M., Melville K., Alexander I.J., Gadd G.M. Role of oxalic acid overexcretion in transformations of toxic metal minerals by Beauveria caledonica. Appl. Environ. Microbiol. 2005; 71(1):371-81. https://doi.org/10.1128/AEM.71.1.371-381.2005
  6. Fomina M., Gadd G.M. Bioremedial potential of metal transformations by fungi. Exploitation of Fungi. Cambridge: Cambridge University Press, 2007. P. 236-254.
  7. Fomina M., Charnock J.M., Hillier S., Alvarez R., Livens F., Gadd G.M. Role of fungi in the biogeochemical fate of depleted uranium. Cur. Biol. 2008; 18(9):R375-R377. https://doi.org/10.1016/j.cub.2008.03.011
  8. Fomina M., BufordE.P., Hillier S., Kierans M., Gadd G.M. Rock-building fungi. Geomicrobiol. J. 2010; 27(6-7):624-629. https://doi.org/10.1080/01490451003702974
  9. Hallberg R., Ferris F.G. Biomineralization by Gallionella. Geomicrobiol. J. 2004; 21(5):325-330. https://doi.org/10.1080/01490450490454001
  10. Ivarsson M., Holmstrom S. The use of ESEM in geobiology. Scanning Electron Microscopy. Shanghai: InTech, 2012. P. 799-818.
  11. Little B., Wagner P., Ray R., Pope R., Scheetz R. Biofilms: an ESEM evaluation of artifacts in troduced during SEM preparation. J. Ind. Microbiol. 1991; 8(4):213-222. https://doi.org/10.1007/BF01576058
  12. Misirli Z., Oner E.T., Kirdar B. Real imaging and size values of Saccharomyces cerevisiae cells with comparable contrast tuning to two environmental scanning electron microscopy modes. Scanning. 2007; 29(1):11-9. https://doi.org/10.1002/sca.20005
  13. Muscariello L., Rosso F., Marino G., Giordano A., Barbarisi M., Cafiero G., Barbarisi A. A critical overview of ESEM applications in the biological field. J. Cell Physiol. 2005; 205(3):328-334. https://doi.org/10.1002/jcp.20444
  14. Tai S.S.W., Tang X.M. Manipulating biological samples for environmental scanning electron microscopy observation. Scanning. 2001; 23(4):267-272. https://doi.org/10.1002/sca.4950230407
  15. Waters M.S., Sturm C.A., El-Naggar M.Y., Luttge A., Udwadia F.E., Cvitkovitch D.G., Goodman S.D., Nealson K.H. In search for the microbe/mineral interface: quantitative analysis of bacteria on metal surfaces using vertical scanning interferometry. Geobiology. 2008; 6(3):254-262. https://doi.org/10.1111/j.1472-4669.2008.00161.x