Study of microbial biofilms using light microscope techniques

Walker, J. T. and Keevil, C. W. (1994) Study of microbial biofilms using light microscope techniques. International Biodeterioration and Biodegradation, 34 (3-4), 223-236. (doi:10.1016/0964-8305(94)90084-1).

Abstract

In industrial ecosystems biofilms can cause severe problems in terms of obstruction, heat transfer, fluid dynamics and corrosion, and so detection of biofilms is therefore important to engineers. Visualisation of biofilms provides a rapid technique for the clarification of biofilm presence. Light microscopy has provided a mechanism of visualising the topology of the biofouling as well as the substrata, identifying particular micro-organisms and determining whether or not the bacteria are viable. Differential interference contrast enabled initial examination of opaque substrata such as copper or stainless steel prior to staining for discrimination of the microorganisms. Subsequent staining of the biofilm with fluorochromes such as acridine orange enhanced differentiation of the micro-organisms against the substrata. Biofilms on galvanised and stainless steel coupons from laboratory chemostat models were exhibited as a heterogeneous film representing a mosaic. This mosaic nature of the biofilm would aggravate localised corrosion by setting up concentration cells. Vital dyes which fluoresce when reduced by metabolising cells have been utilised to determine the viability of bacteria within biofilms on coupons from laboratory models, as well as industrial samples after microbial control measures have been instigated. The position of the waterborne human pathogen Legionella pneumophila has been identified within biofilms with the use of direct labelling probes. The light microscope was equipped with various fluorescent filter combination blocks to enable different strains to be used simultaneously and with the use of long working distance lenses the specimen are not compressed.

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Contributors

Author: C. W. Keevil

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