STUDY OF MICROBIAL BIOFILMS USING LIGHT-MICROSCOPE TECHNIQUES

In industrial ecosystems biofilms can cause severe problems in terms o f obstruction, heat transfer, fluid dynamics and corrosion, and so det ection of biofilms is therefore important to engineers. Visualisation of biofilms provides a rapid technique for the clarification of biofil m presence. Light microscopy has provided a mechanism of visualising t he topology of the biofouling as well as the substrata, identifying pa rticular micro-organisms and determining whether or not the bacteria a re viable. Differential interference contrast enabled initial examinat ion of opaque substrata such as copper or stainless steel prior to sta ining for discrimination of the microorganisms. Subsequent staining of the biofilm with fluorochromes such as acridine orange enhanced diffe rentiation of the micro-organisms against the substrata. Biofilms on g alvanised and stainless steel coupons from laboratory chemostat models were exhibited as a heterogeneous film representing a mosaic. This mo saic nature of the biofilm would aggravate localised corrosion by sett ing up concentration cells. Vital dyes which fluoresce when reduced by metabolising cells have been utilised to determine the viability of b acteria within biofilms on coupons from laboratory models, as well as industrial samples after microbial control measures have been instigat ed. The position of the waterborne human pathogen Legionella pneumophi la has been identified within biofilms with the use of direct labellin g probes. The light microscope was equipped with various fluorescent f ilter combination blocks to enable different strains to be used simult aneously and with the use of long working distance lenses the specimen ave not compressed. Thus light microscopy provided a rapid means of d etermining the presence and viability of bacteria in biofilms with min imum disruption of the microbial specimen.