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S T Williams

Publications and source records attributed to S T Williams.

At least 55 records · Page 3Linked to original sources
PubMed1978

The influence of pH on the growth rate and viability of neutrophilic and acidophilic streptomycetes.

The influence of pH on the specific growth rates of two acidophilic and two neutrophilic soil streptomycetes was studied. The acidophiles had maximum growth rates over a broad range from pH 4.5 to 5.5, while the neutrophiles had clearly defined optima at pH 7.0. Mycelium of neutrophiles was less tolerant of acidity than that of acidophiles; both showed decreased viability at pH levels below those which allowed growth. Spores of neutrophiles and acidophiles were equally tolerant of acidity and this may allow the former to survive in acid soils. Both spores and mycelium of acidophiles remained viable at pH levels above those allowing growth.

Hydrogen-Ion Concentration↗
PubMed1978

The influence of pH on starch hydrolysis by neutrophilic and acidophilic streptomycetes.

The effect of pH on the starch hydrolysing activity of one neutrophilic and two acidophilic soil streptomycetes was studied in detail. The neutrophilic culture extract was active from pH 5.0 to pH 8.0, with optimum activity from pH 5.5 to 6.5. Acidophile activity occurred from pH 2.5 to 7.0 with an optimum at pH 4.0 to 4.5. After storage for 24 h at different pH levels, neutrophiles showed a sharp reduction in activity at pH 5.0 with none below this point; some activity was maintained up to pH 10.0. Acidophiles remained active after storage at pH 3.0 and retained some activity up to pH 7,0--9.0. Less detailed tests on a range of soil streptomycetes showed that the differences between acidophiles and neutrophiles were consistent. The results indicated that acidophilic streptomycetes may produce a range of exo-enzymes which are themselves acid-requiring and play an important part in decomposition processes in acidic soils and litters.

Amylases↗
PubMed1977

Effects of addition of chloramphenicol on the growth and ultrastructure of Streptomyces venezuelae.

The effects of adding chloramphenicol before inoculation and during exponential growth of Streptomyces venezuelae (3022a) in fermentors were studied. The responses of the organism during synthesis of chloramphenicol (in a glycerol-serine-lactate medium) were compared with those in media supporting less (glycerol-nutrient broth-yeast extract) or no synthesis (glucosemineral salts). In systems where little or no synthesis of the chloramphenicol occurred, addition of the antibiotic induced micromorphological and ultrastructural abnormalities similar to those reported for sensitive bacteria. There was also an increase in the frequency of mesosomes and electron-light areas. It was suggested that the former may be associated with activity of chloramphenicol hydrolase and the latter with storage and/or excretion of the breakdown product; N-acetyl p-nitro-phenylserinol. When chloramphenicol synthesis occurred, addition of the antibiotic had less effect on the micromorphology or ultrastructure of S. venezuelae as permeability barriers to external chloramphenicol had been established. Electron-light areas were frequent, possibly being associated with storage and excretion of precursors of chloramphenicol.

Cell Membrane↗
PubMed1976

Growth and ultrastructure of Streptomyces venezuelae during chloramphenicol production.

Streptomyces venezuelae (3022a) was grown in flask cultures and fermentors, using three media having differential effects on chloramphenicol production. Micromorphology, ultrastructure and chloramphenicol concentrations were studied during the growth cycle in each medium. Chloramphenicol production was greatest in the glycerol-serine-lactate (GSL) medium, less in the glycerol-nutrient broth-yeast extract (GNY) medium and very low in glucose-mineral salts (GA) medium. In GSL and GA, much growth was in the form of microcolonies, especially in flask cultures, while short hyphal fragments predominated in GNY. The major ultrastructural features were the high frequency of mesosomes in fragmenting hyphae in GNY, and electron-transparent zones which appeared during chloramphenicol synthesis in GSL. None of the structural abnormalities induced by chloramphenicol in sensitive organisms were observed in S. venezuelae despite high levels of the antibiotic in GSL medium.

Cell Membrane↗
PubMed1976

Chemical composition of the spore sheath of Streptomyces griseus.

The fibrillar sheath surrounding spores of Streptomyces griseus was separated from spores and partially purified by differential centrifugation. The reaction of isolated sheath material to various solvents and enzymes was monitored by electron microscopy. Fibrilar elements (rodlets) were apparently resistant to most solvents and enzymes used; only acetone induced any change in their appearance. Analysis of sheath material showed that its composition differed considerably from that of spore walls, having a low content of nitrogen (1.7% w/w), amino sugars (0.067% w/w) and carbohydrate (0.036% w/w). It was suggested that the sheath may be at least partially inorganic in nature.

Amino Sugars↗
PubMed1976

Development and fine structure of sclerotia and spores of the actinomycete Chainia olivacea.

Sclerotia and spores of Chainia olivacea were studied by transmission and scanning electron microscopy. Sclerotia formed by repeated branching of several hyphea. Branch tips were delimited by septa and increased in size, becoming filled with lipid-like inclusions. In mautre sclerotia, empty cells and intra-hyphal growth were observed. An electron-dense fibrillar material was deposited between hyphae and on the sclerotium surface. The similarities between these and the sclerotia of certain fungi are discussed. Spores were formed in a manner similar to that in Streptomyces species. Large inter-sporal pads were formed during ingrowth of the septa delimiting the spores.

Cell Wall↗
PubMedDate not supplied

Staging of colorectal cancer.

A chronological overview of the various staging systems for colorectal cancer is presented in an effort to demonstrate the reason for the current state of confusion. The Dukes 1932 system is considered to be the gold standard because of its simplicity and accuracy and is the system most often referred to in the literature. Number of positive nodes and depth of invasion are two variables that have been found to be predictors of survival. In the future, other prognostic factors such as nuclear morphology, flow cytometric characteristics, histological grade, and vascular or lymphatic invasion may also be entered into the staging equation. Use of the TNM system at this time is recommended since it most completely describes appropriate prognostic factors and allows conversion of other staging systems into a common format. Future modifications could logically evolve from the TNM system.

Colorectal Neoplasms↗