Susceptibility and Resistance of Several Fungi to Microbial Lysis

Abstract

Streptomyces, Nocardia, and Pseudomonas capable of lysing hyphae of Fusarium solani or Neurospora crassa were obtained by selective culture, but attempts to isolate an organism lysing Rhizoctonia solani failed. When provided with F. solani or N. crassa as carbon sources, the actinomycetes tested produced f3-(1-* 3) glucanase and chitinase. A mixture containing purified chitinase and (3-(1-, 3) glucanase induced spheroplast formation in F. solani, caused some morphological changes in N. crassa, but had almost no effect on R. solani hyphae. The polysaccharides in R. solani walls, which contain a large amount of glucose as well as galactose, mannose, and glucosamine, were not hydrolyzed appreciably by the two enzymes. Laminaribiose and laminaritriose were released by enzymatic hydrolysis of F. solani and N. crassa walls, and gentiobiose was liberated from R. solani and N. crassa walls. Melaninlike materials were found in R. solani walls, accounting for

The contribution of melanin to microbial pathogenesis

“…Enzymatic degradation is inhibited by melanin in moulds, including Rhizoctonia spp. (Lockwood, 1960;Potgieter and Alexander, 1966;Bloomfield and Alexander, 1967), Sclerotinia spp. (Lockwood, 1960;Bloomfield and Alexander, 1967), Verticillium sp.…”

Extracellular enzyme localization during interspecific fungal interactions

“…The initial products of oxidation are usually o-quinones, which being highly unstable, undergo polymerization to yield dark melanin-like pigments of high molecular mass. The relationship between the presence of melanin, or melanin-like pigments in fungi and resistance to microbial lysis has been demonstrated [20][21][22][23][24][25]. Bull [25] reported that melanins can function as a physical barrier, preventing access by cell wall-degrading enzymes of other organisms.…”

The Survival of Fungal Sclerotia Under Adverse Environmental Conditions

“…Chet et al (1967) found that sclerotial walls of Sclerotium rolfii contain a melanin-like pigment which is absent from hyphal walls and they suggested that this pigment is important in providing resistance to biological and chemical degradation. Support for this has been given by Potgieter & Alexander (1966) (i) The chitin and probably also the glucans and other components of the hyphal wall are protected by the melanin secreted by the protoplast, either as a deposit on the outer surface of the hyphae and/or by the formation of a complex, particularly with chitin, in the cell wall.…”

“…Some fungi are particularly susceptible to lysis by other micro-organisms while others are resistant to microbial degradation. Chlamydospores and sclerotia are particularly resistant (Potgieter & Alexander, 1966) as are the pigmented hyphae of Helminthosporium sativum, Rhizoctonia solani and Alternaria solani (Lockwood, 1960). Much evidence indicates that melanin or related substances may have great ecological significance in reducing damage by the lytic action of micro-organisms.…”