Autolytic Phase Of Growth Research Articles

Biochemical changes in the mycelium of two Rhizoctonia solani isolates during autolysis

Some biochemical changes occurring in the mycelium of two isolates (one pathogenic FR and another non-pathogenic GD2) of <i>R. solani</i> during autolytic phase of their growth were studied, by growing the fungi for periods longer than 210 days. During autolysis a decrease of 76.4% and 78.5% in mycelial dry weight occurred in pathogenic and non-pathogenic isolates respectively, compared to that at the beginning of autolysis. The mycelium of non-pathogenic isolate was more affected during autolytic phase of growth than that of the pathogenic isolate.

Asexual sporulation signalling regulates autolysis ofAspergillus nidulansvia modulating the chitinase ChiB production

Elucidation of the regulation of ChiB production in Aspergillus nidulans. Mutational inactivation of the A. nidulans chiB gene resulted in a nonautolytic phenotype. To better understand the mechanisms controlling both developmental progression and fungal autolysis, we examined a range of autolysis-associated parameters in A. nidulans developmental and/or autolytic mutants. Investigation of disorganization of mycelial pellets, loss of biomass, extra-/intracellular chitinase activities, ChiB production and chiB mRNA levels in various cultures revealed that, in submerged cultures, initialization of autolysis and stationary phase-induced ChiB production are intimately coupled, and that both processes are controlled by the FluG-BrlA asexual sporulation regulatory pathway. ChiB production does not affect the progression of apoptotic cell death in the aging A. nidulans cultures. The endochitinase ChiB plays an important role in autolysis of A. nidulans, and its production is initiated by FluG-BrlA signalling. Despite the fact that apoptosis is an inseparable part of fungal autolysis, its regulation is independent to FluG-initiated sporulation signalling. Deletion of chiB and fluG homologues in industrial filamentous fungal strains may stabilize the hyphal structures in the autolytic phase of growth and limit the release of autolytic hydrolases into the culture medium.

Behaviour of the cell walls of Aspergillus niger during the autolytic phase of growth

Behaviour of the cell walls of Aspergillus niger during the autolytic phase of growth

Lytic enzymes in autolysis ofBotrytis cinerea

Filamentous fungi produce during their autolytic phase of growth lytic enzymes which can catalyze the degradation of cell-wall polysaccharides [1] and cytoplasmic material [2] and are considered important in pathogenesis [3]. These enzymes show increased activity in the culture fluid during autolysis [4-6] and also occur in the mycelium [ 1,7,8]. Many studies have been made on pectic enzymes, cellulases and xylanases produced by Botrytis cinerea and the role they play in pathogenic processes [9-12]. Recently enzymes degrading plant cell-wall polysaccharides present during the autolysis of Botrytis cinerea have been studied [131. This paper describes the changes in the activities in the culture fluid and in the mycelial extract of the lytic enzymes implicated in the degradation of the cell wall of this fungus during the autolytic phase of growth.

Lytic enzyme activity in autolysing mycelium of Aspergillus niger.

We have studied changes in the activity of some lytic enzymes contained in mycelium of Aspergillus niger in cultures relative to the autolytic phase of growth. Acid phosphatase, polygalacturonidase and alpha-amylase activity reached its highest level (40.7, and 8 U/sample, respectively) at the initiation of the autolytic phase of growth. 1.3-beta-Glucanase and beta-N-acetylglucosaminidase reached its highest level (3.5 and 2 U/sample, respectively) during the first days of autolysis. Alkaline phosphatase, cellulase, invertase, esterase, chitinase and proteolytic activity is also present in autolysing mycelium of A. niger, though comparatively low. Their maximum activity coincided with the beginning of the autolytic phase of growth. In all enzymes studied here, as autolyis proceeded, enzyme activity decreased by about 90%. Only esterase activity remained nearly constant throughout the whole period of autolysis described here.

Cell wall plant polysaccharide-degrading enzymes in autolysis of Botrytis cinerea

The mycelium of Botrytis cinerea undergoes a loss of 80% of its dry weight during the autolytic phase of growth in culture. The activities of lytic enzymes (polygalacturonase, endo-polygalacturonase, polymethylgalacturonase, endo-polymethylgalacturonase, pectin lyase, endo-pectin lyase, pectin esterase, xylanase, exo-cellulase and endo-cellulase) directly implicated in the degradation of plant cell walls were always higher in the culture liquid than in the mycelial extracts. Enzyme activities in the culture liquid increased during autolysis then decreased slightly at the end of this period, except for pectin esterase and polymethylgalacturonase which disappeared. With the exception of endopectin lyase, activities in the mycelial extract decreased and eventually disappeared during or at the end of the autolysis. Pectate lyase and endo-pectate lyase were not evident. The enzymatic complex obtained from autolyzed cultures of B. cinerea produced maceration of tissues, death of the cells and attack on bean plants.

Lytic enzymes in the autolysis of Schizophyllum commune with special reference to 1,3-alpha-glucanase.

In the autolytic phase of growth Schizophyllum commune lost 62% of its dry weight in 70 days of incubation. The variations in the activity of some lytic enzymes were studied in the culture fluid and mycelial extracts during growth and autolysis of this fungus. The enzymes 1,3-beta-glucanase (exoglucanase), 1,3(4)-beta-glucanase (endoglucanase), alpha-amylase, and invertase behaved in the same way in culture fluid and mycelial extract, but their activities were much higher in the culture fluid. The enzyme activities increased during autolysis, but then decreased at the end of this period except in the case of alpha-amylase which remained high. It was only possible to detect 1,6-beta-glucanase, cellulase, and polygalacturonase activities at certain times during the autolytic phase of growth. The enzyme chitinase was not detected and 1,3-alpha-glucanase (S-glucanase) occurred in the mycelial extract at a higher concentration than in the culture fluid. A decrease in the activity of this enzyme in the mycelial extract and an increase in the culture fluid occurred during autolysis. The enzyme 1,3-alpha-glucanase exhibited two optima pH, one at 6.0 and the other at 8.0. The Km value for the latter was 0.02 M at pH 5.5 in borate-citrate-phosphate buffer.

Effect of the level of the carbon source on the activity of some lytic enzymes released during autolysis of Aspergillus niger

Changes in the activity of β-N-acetylglucosaminidase, chitinase, invertase, esterases, glucanases and phosphatases liberated into the culture fluid were followed during the autolytic phase of growth of Aspergillus niger on media with various initial levels of the carbon source. The general pattern was of an accumulation of these lytic enzymes in the culture fluid during autolysis, but some enzymes reached maximum activity and then declined. The initial level of the carbon source affected the enzyme pattern during autolysis. Maximum activity for the various enzymes was always observed either for the lowest initial level of carbon or the highest (3.5 mM glucose, 111 mM glucose). The highest specific activities were those for exopolygalacturonidase (500 mU/mg at 3.45 mM glucose), and for α-amylase (about 500 mU/mg at 3.45 mM glucose). Cellulase, chitinase and esterase showed the weakest activity. Acid phosphatase was most active (about 200 mU/mg) at 3.45 mM initial glucose, whereas alkaline phosphatase was most active (45 mU/mg) at 111 mM glucose, both during the autolytic phase of growth.

Influence of Temperature on the Autolytic Phase of Growth of Aspergillus niger

Influence of Temperature on the Autolytic Phase of Growth of Aspergillus niger

Biochemical Changes in Cultures of Nectria galligena during the Autolytic Phase of Growth

Some biochemical changes occurring in cultures of Nectria galligena during its autolytic phase of growth have been investigated. In nitrate-grown and autolysed cultures of this fungus the degree of autolysis amounted to 57 per cent. The amount of mycelial lipids decreased continuously with the age of the culture. Total mycelial nitrogen did not substantially change within the first 50 days of autolysis. The constancy in the amount of bound amino acids released from mycelium of Nectria galligena strongly suggests that mycelial protein are not affected by autolysis.