摘要:

Bacteria isolated from surfaces of conidia ofCochliobolus sativusincubated in soil were tested for their antagonistic effect on the pathogen, and their ability to degrade fungal cell wall components such as proteins, chitin, lipids, or cellulose. Of the 22 isolates tested only 12 utilized intact conidia as sole nutrient source, and 3 grew poorly on isolated conidial walls. The ability of the various bacteria to colonize conidiain vitrowas not correlated with their hydrolytic capacity, or with production of exopolysaccharides. Also, the hydrolytic properties exhibited by the bacteria that were isolated from the surface of conidia were not significantly different from those isolated directly from soil. Motile isolates were not attracted to intact conidia when examined in chemotaxis tests, but they often adhered to the spore surface when in close proximity. The ability of bacteria to adhere to the spores correlated with their ability to grow on intact conidia. Some of the bacterial colonizers of the conidia were identified as species ofBacillus,Pseudomonas,Arthrobacter, andStreptomyces. The antagonistic effect of each of these bacteria to the fungus was tested on agar plates. Five of the isolates were also tested for their antagonism of conidia in soil by coincubation. The inhibition of fungal growth observed on agar tests did not correlate with the inhibition of conidial germination after the spores were incubated with bacteria in soil. The inhibitory effect imposed on the conidia by bacteria seemed to be modified by the soil microflora.

ISSN:0008-4166    

DOI:10.1139/m85-077

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Group B streptococci treated with cell wall synthesis inhibitors (penicillin or vancomycin) or by a variety of membrane-acting agents are sensitized to the lytic action of exogenous M1 muramidase. Muramidase without a sensitizing agent caused rupture of bacterial chains only, accompanied by the release of a small amount of cell wall peptidoglycan label and an increase of the number of colony-forming units. In combination with sensitizing agents the exogenous muramidase appeared to initiate hydrolysis of biosynthetically new peptidoglycan. Treatment of the cells with chloramphenicol or starvation for nutritionally required amino acids suppressed the rate of cell lysis and peptidoglycan hydrolysis during subsequent sensitization and muramidase treatment of the bacteria. Purified cell walls prepared from the amino acid starved cells were also hydrolyzed with a slower rate by muramidase. It is suggested that agents sensitizing the bacteria to the exogenous muramidase act by perturbing or removing some nonmurein components of the cell envelope which protect the peptidoglycan from the activity of exogenous enzyme. Agents increasing resistance against exogenous muramidase may also cause some alteration in peptidoglycan structure.

ISSN:0008-4166    

DOI:10.1139/m85-078

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Sexual development leading to macrocyst formation inDictyostelium discoideuminvolves the development of zygote giant cells which subsequently chemoattract and cannibalize local unfused amoebae of the same genotypes from which they formed. A system for assessing this process was developed wherein purified giant cells were fed amoebae under various conditions with the production of endocytes being assessed after neutral red staining of living cells. The phagocytic rate was linear during the 3-h assay period, was directly related to the concentration of amoebae, and demonstrated limited pH and temperature optima. Light which inhibits macrocyst development had no effect on sexual endocytosis. Cell-free conditioned medium from sexual cultures actively involved in phagocytosis enhanced giant cell endocytosis in the assay system. Drug studies revealed that microfilaments and microtubules are involved in the endocytic process and energy for it is supplied by both aerobic and anaerobic metabolic pathways. The data are discussed in terms of phagocytosis inD.discoideumand other organisms.

ISSN:0008-4166    

DOI:10.1139/m85-079

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Mutants ofBacillus subtiliswhich carried suppressor mutations for catabolite-resistance genecrsA47were isolated from methylmethanesulfonate-treated cultures of GLU-47 (crsA47). The suppressor mutation,sca19, suppressed resistance ofcrsA47mutant to glucose and other inhibitors of sporulation. Moreover, the suppressor mutation could restore the rate of growth and the level of IMP dehydrogenase and alkaline phosphatase ofcrsA47mutant to the wild-type level. Thesca19mutation was also able to suppress catabolite resistance of othercrsmutants. The map position of thesea19mutation indicated that this mutation was an intergenic suppressor for thecrsmutants. It was also found that an erythromycin-resistance mutation,ery1, could suppress the catabolite resistance of some of thecrsmutants. Our results were discussed in relation to the importance of a proper state of metabolic activities and membrane functions during the initiation of sporulation.

ISSN:0008-4166    

DOI:10.1139/m85-080

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A process for the production of citric acid from canola (rapeseed) oil using the yeastSaccharomycopsis lipolyticawas examined. A citrate nonutilizing strain, designated NTG9, which had an improved citric to isocitric acid ratio, was isolated after mutagenesis ofS.lipolyticaATCC 20228 with nitrosoguanidine. Although the mutant grew well on canola oil, unlike the parent strain or a spontaneous revertant (JF2), it did not grow on glycolytic intermediates below glycerate-3-phosphate, amino acids, hexadecane, or yellow kerosene. The mutant was shown to be impaired in the gluconeogenic pathway because of a loss of phosphoenolpyruvate carboxykinase activity. A preliminary study of the effect of micronutrients on citric acid production byS.lipolyticaNTG9 showed that manganese had a stimulatory effect on the process whereas zinc and iron were inhibitory. A revised growth medium was tested and found to increase citric acid production while decreasing that of isocitric acid.

ISSN:0008-4166    

DOI:10.1139/m85-081

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Several oximes, acetohydroxamic acid, and 3-nitropropionic acid were examined to determine if they could serve as substrates for heterotrophic nitrification by anAlcaligenessp., previously isolated from soil and shown to actively nitrify pyruvic oxime. Neither acetohydroxamic acid, the aldoximes of acetaldehyde or butyraldehyde, or the alkyl oxime, acetone oxime, were used as nitrification substrates or as sole sources of carbon or nitrogen. α-Ketobutyric oxime, α-ketoglutaric oxime, and 3-nitropropionic acid, however, were nitrified and growth occurred when these compounds served as sole sources of carbon and nitrogen. Experiments with resting cells and cell-free extracts of theAlcaligenessp. grown on α-ketobutyric oxime and α-ketoglutaric oxime indicate that these substrates are nitrified via an organic pathway as the rates of hydroxylamine (the nitrogen hydrolysis product) conversion are kinetically insufficient. 3-Nitropropionic acid metabolism by resting cells of theAlcaligenessp. grown in 3-nitropropionic medium is restricted to nitrite production. The substrate specificities of theAlcaligenessp. for heterotrophic nitrification and the relevance of the mineralization of 3-nitropropionic acid by the bacterium are discussed.

ISSN:0008-4166    

DOI:10.1139/m85-082

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Cellophane cultivation techniques have been proven to be useful for the study of colony growth inStreptomyces. Results obtained by this procedure indicate that, inS.antibioticus, substrate mycelium was a nutrient support for aerial mycelium growth. Oleandomycin synthesis starts before aerial mycelium formation and may play an important role during colony growth.

ISSN:0008-4166    

DOI:10.1139/m85-083

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A number of yeasts that produce ethanol fromD-xylose also coproduce xylitol. Such coproduction is undesirable if ethanol is the desired product because of the detrimental effect on yield. The utilization of xylitol, thought to be the first catabolite ofD-xylose, has been reported not to lead to the formation of appreciable amounts of ethanol. As part of an effort to improve the yield of ethanol, the use of xylitol for growth and ethanol formation byPachysolen tannophilusunder aerobic conditions was reinvestigated. The polyol was found to be used for ethanol formation. However, the conditions required for this process, as well as for growth, were more stringent than withD-xylose. Notably, xylitol supported growth only when its concentration was relatively high, while ethanol formation occurred over a range of concentrations, provided high cell densities were used.

ISSN:0008-4166    

DOI:10.1139/m85-084

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Five strains ofHaemophilus pleuropneumoniae, out of eight strains tested, produced extracellular haemolysin(s) when grown in liquid culture in the presence, but not in the absence, of RNA. The haemolysin produced by the neotype strain was unstable, heat labile, and sensitive to degradation by pronase, trypsin, and chymotrypsin; moreover, trypan blue treated haemolysin preparations were less effective at causing erythrocyte lysis than were untreated preparations. Following growth in the absence of RNA, washed suspensions of the neotype strain produced extracellular haemolysin when incubated in the presence of RNA, glucose, and casein acid hydrolysate; extracellular haemolysin could not be detected if the incubation mixture contained chloramphenicol. The haemolysin produced by washed bacterial suspensions was similar to that produced by growing cultures in that it was unstable, heat labile, and sensitive to inactivation by the same complement of enzymes. Erythrocyte lysis induced by either haemolysin preparation was preceded by a prelytic phase, the duration of which was dependent upon haemolysin concentration and the initial temperature of the haemolysin–erythrocyte mixture. It is concluded that the haemolysin(s) produced by the neotype strain ofH.pleuropneumoniaeis distinct from, but closely related to both streptolysin S and the haemolysin produced byTreponema hyodysenteriae.

ISSN:0008-4166    

DOI:10.1139/m85-085

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The lipid composition of an obligately anaerobic bovine rumen fungusNeocallimastix frontalis, belonging to the Neo-callimasticaceae of the Chytridiomycetes, has been investigated. It consisted of 44% neutral lipids (triacylglycerol, fatty acid, and sterols) and 56% polar lipids. The fatty acid composition of this unusual fungus differed markedly from that of other members of Chytridiomycetes by the absence of long-chain polyenoic fatty acids and by the presence of a large proportion (48%) of a series ofcis-monoenoic fatty acids between 14:1 and 24:1. The absence of polyunsaturated fatty acids is explained by the anaerobic life style of this organism. However, the formation of the large proportions of monoenoic fatty acids under anaerobic conditions constitutes a major difference which cannot be explained by known pathways of fatty acid biosynthesis in fungi. This result indicates thatN.frontalisdiffers from other fungi in possessing an anaerobic pathway for monoenoic fatty acid biosynthesis.

ISSN:0008-4166    

DOI:10.1139/m85-086

出版商:NRC Research Press    

年代:1985

数据来源: NRC