Non-nutritive Surfaces Research Articles

Hydrophobic nature and effects of culture conditions on biofilm formation by the cellulolytic actinomycete <em>Thermobifida fusca</em>

<em>Thermobifida fusca</em> produces a firmly attached biofilm on nutritive and non-nutritive surfaces, such as cellulose, glass, plastic, metal and Teflon^&reg;. The ability to bind to surfaces has been suggested as a competitive advantage for microbes in soil environments. Results of previous investigations indicated that a Gram-positive cellulolytic soil bacteria, <em>Cellulomonas uda</em>, a facultative aerobe, specifically adhered to nutritive surfaces forming biofilms, but cells did not colonize non-nutritive surfaces. Cell surface hydrophobicity has been implicated in the interactions between bacteria and the adhesion to surfaces. It was recently described that the cellulolytic actinomycete <em>T. fusca</em> cells hydrophobicity was measured and compared to the cellulolytic soil bacteria <em>C. uda.</em> Also, <em>T. fusca</em> biofilm formation on non-nutritive surface, such as polyvinyl chloride, was examined by testing various culture ingredients to determine a possible trigger mechanism for biofilm formation. Experimental results showed that partitioning of bacterial cells to various hydrocarbons was higher in <em>T. fusca</em> cells than in <em>C. uda</em>. The results of this study suggest that the attachment to multiple surfaces by <em>T. fusca</em> could depend on nutrient availability, pH, salt concentrations, and the higher hydrophobic nature of bacterial cells. Possibly, these characteristics may confer <em>T. fusca</em> a selective advantage to compete and survive among the many environments it thrives.

Biofilm formation in the life cycle of the cellulolytic actinomycete Thermobifida fusca

ABSTRACTActinomycetes have been used with enormous success in industrial processes; however, little is known about biofilm formation by these filamentous microbes, or community development on insoluble substrates such as cellulose. We hypothesized that biofilm formation is a general strategy used by actinomycetes in the degradation of cellulose, and that it may serve as a means for these microbes to secure nutrients and persist in their environments. The objective of this study was to examine biofilm production byThermobifida fusca, an actinomycete that rapidly degrades cellulose by means of a well-characterized extracellular cellulase system.Thermobifida fuscacells grew as biofilms attached to both nutritive (e.g. dialysis tubing membrane) and non-nutritive surfaces. Dialysis tubing was colonized byT. fuscaaleuriospores but not by mycelial pellets, except when mycelial pellets were disrupted by sonication. Microscopic examination of surface-attached growth revealed structures characteristic of biofilms, with cells embedded in fibrous material suggestive of an extracellular polymeric matrix. Concanavalin A bound to the extracellular polymeric substance of biofilms and mycelial pellets, indicating alpha-linkedd-mannosyl and/or alpha-linkedd-glucosyl residues. The carbohydrate content of both biofilms and mycelial pellets increased during growth. Also, DNase I inhibited biofilm production, suggesting a role for extracellular DNA inT. fuscabiofilm development. Cellulose degradation and expression ofcelE(encoding endoglucanase E5) was similar forT. fuscabiofilms and mycelial pellets. Results of this study indicate that, in the life cycle of this actinomycete, cellulose is specifically colonized by aleuriospores, which germinate, grow and degrade cellulose, ultimately developing into biofilms encased in a carbohydrate-containing exopolymeric matrix, a hallmark of biofilm production.

Translocation of solutes along rhizomorphs of Armillaria mellea

A procedure is described for producing rhizomorphs of Armillaria mellea in the laboratory so that they can be used to study translocation of [ 3 H], [ 14 C] and [ 32 P] along them while they are in contact with non-nutritive surfaces. The data obtained indicate that diffusion can be ruled out as a mechanism of translocation. The velocity of translocation of radio-activity has been estimated to be 0.55–10.8 cm h −1 and the flux of carbohydrate (taken as glucose) 0.07–3.8 nmol cm −2 s −1 with the flux of phosphorus of a similar order of magnitude. The form in which the carbohydrate is translocated has proved to be difficult to identify due to presumed lateral transfer of label from the translocation stream into other parts of the rhizomorph and metabolic compartmentation away from the stream.

Effect of naturally occurring apatites on growth and morphology of algae.

Crystals (30--100 micrometer) of selected naturally occurring apatite (Ca10 (PO4)6(OH, F)2) samples were added to P-free (less than 0.001 microgram/ml total P) Bristol's medium (1-1000 microgram/ml of apatite) as the sole source of ortho-PO43-. The media were inoculated with washed, non-axenic cells of three chlorophycean algal species cultivated under PO43--deficient conditions. Phase-contrast and scanning electron microscopy revealed that at low slurry densities (1-10 microgram/ml of apatite), Ankistrodesmus braunii (ATCC 2744) cells were morphologically distorted. At concentrations of 100 and 1000 microgram/ml of apatite, more than 85% of the cells had undergone autospore formation within 7--10 days of incubation at 20 degrees C. Most autospores formed failed to germinate under high nutrient conditions. Scenedesmus longus (No. 1236) formed colonies when cultivated in Bristol's medium but daughter cells displayed a Chodatella-like unicellular morphology when grown in apatite media. Test algal species (Chlamydomonas dysosmos, S. longus, A. braunii) showed a marked preference for growth on apatite crystals over non-nutritive surfaces. Unialgal and mixed-algal cultures produced an extensive matrix of extracellular fibrous material in response to growth on crystals at concentrations greater than 10 microgram/ml of apatite.

Some effects of atmospheric humidity on the growth of Serpula lacrimans

Blocks of seasoned sapwood of Pinus sylvestris were infested with Serpuda lacrimans ([Wulf.] Fr.) Schroeter, then held at 20°C in an apparatus in which the ends of the blocks were exposed to atmospheres of known r.h., while the centre of the block was supplied with unlimited water. In these conditions the fungus grew out from the wood for substantial distance over a non-nutritive surface at humidities between 100 and 95%. It grew only slightly at 90% r.h. and not at all at humidities of 82% and below.