Attachment of Marine Microorganisms to Surfaces

Boney, Andrew James Victor (1991) Attachment of Marine Microorganisms to Surfaces. MSc(R) thesis, University of Glasgow.

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The attachment mechanisms of the main groups of marine microorganisms are similar. These similarities are particularly shown by the nature of the adhesive mucilages they produce. Marine bacteria, cyanobacteria and diatoms produce acidic polysaccharide mucilages. Macroalgal spores attach by the production of glycoprotein adhesives. The spores of several marine Ascomycete fungi attach by means of mucilaginous, fibrillar appendages, although little is known about their composition. Certain marine bacteria possess cell-surface structures such as stalks with holdfasts, flagella and spinae which may play an attachment role. Cyanobacteria possess pili and spinae which may serve the same purpose. The formation of proteinaceous conditioning films on substrata promotes bacterial adhesion. Polymeric polysaccharide materials and bacterial films also precondition surfaces for algal attachment. Substratum properties such as wettability and surface free energy can affect, and in some cases decrease, levels of bacterial and algal attachment. Marine microbial adhesion is of importance in disease pathogenesis, biotic interactions, physical interactions and certain economic aspects. In disease pathogenesis, the attachment of Aeromonas salmonicida to fish cells by the 'A'-protein layer is important in the initiation of furunculosis. Some invertebrate diseases are also caused by attached microorganisms. The bacterium Leucothrix mucor, along with diatoms, cyanobacteria and protozoa can accumulate on the gills of shrimps, crabs and lobsters. This heavy infestation causes death by suffocation. Vibrio cholerae attaches to the oral region of planktonic copepods and the hindgut of the blue crab Callinectes sapidus. These observations may be important for the epidemiology of cholera in aqueous environments. Microbial attachment may also be important in the establishment of symbiotic relationships with certain marine invertebrates. Biotic interactions include the formation of primary microbial films on any new surface immersed in seawater. Extensive microbial epiphytic layers form on seaweeds and estuarine salt marsh grasses. Bacteria which attach to the heterocysts of the cyanobacterium Anabaena spp. in the freshwater environment could be involved in nitrogen fixation. The parasitic marine bacterium Bdellovibrio bacteriovorus attaches to host cell membranes by cell-surface fibres, which ultimately leads to cell lysis. Attached bacteria are responsible for the aggregation of particulate detritus, which eventually disaggregates due to protozoal activity. Bacteria utilize dissolved organic carbon for the formation of adhesive materials which cause detrital aggregation. The attachment of bacteria to certain phytoplankton, including diatoms, ultimately results in the formation of amorphous detrital aggregates. Physical interactions include microbial attachment to sediments. Microbial attachment and adhesive production is important in the formation of microbial mats. Marine bacteria, cyanobacteria and diatoms are abundant in these mats. Microbial extracellular polymer material is responsible for lamination of mat layers and the structural integrity of the mats. Gelatinous mats are often formed in sediments from microalgal adhesive secretions. These mats are of importance in sediment stabilization. The adhesive mucilages of certain diatoms also reduce the resuspension of sediment particles. Microbial extracellular materials may also be utilized as a food source by benthic invertebrates. One economic aspect of marine microfouling is metal corrosion. Corrosion can result from the formation of differential aeration cells under a non-uniform film of attached microorganisms. Sulphate-reducing bacteria, which are often present in biofilms under anaerobic conditions corrode metals by cathodic depolarization. This process allows the formation of corrosive hydrogen sulphide and iron sulphide from sulphates. Some diatoms, such as Amphora spp., may inhibit corrosion by forming a uniform layer of adhesive mucilage over a metal surface. A further economic aspect is the affect of microbial attachment on the development of antifouling techniques. Bacterial and diatom slime films are easily formed on cuprous oxide and organometallic antifouling paints. This makes them less effective. The effects of surface free energy and wettability of substrata on bacterial and algal adhesion could provide a further antifouling technique. Conditioning film formation can alter these substratum properties towards a biocompatible range where lower rates of microfouling occur. The incorporation of silicone elastomers in substrata also decreases bacterial and diatom attachment. The use of metabolic inhibitors or calcium chelating agents to remove bacterial and diatom films could be a further antifouling development.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Zoology, Biological oceanography, Microbiology
Date of Award: 1991
Depositing User: Enlighten Team
Unique ID: glathesis:1991-78287
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09

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