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Biomedical subjects

A A Yousten

Publications and source records attributed to A A Yousten.

At least 37 records · Page 2Linked to original sources
PubMed1982

Ultrastructural Analysis of Spores and Parasporal Crystals Formed by Bacillus sphaericus 2297.

Bacillus sphaericus 2297, growing from a boiled, relatively nontoxic spore inoculum, increased about 30-fold in toxicity for mosquito larvae during early exponential growth but showed an approximately 1,000-fold toxicity increase during the late-exponential phase, as spores began to appear in the culture. The development of spores in the bacterial cells was accompanied by the formation of parasporal crystals. These parasporal crystals appeared during stage III as the forespore septum engulfed the incipient forespore. The paraspores were separated from the forespores by a branch of the exosporium across the cell. Measurements of the parasporal substructure revealed a 6.3-nm distance between the striations. When spores and paraspores were fed to mosquito larvae and the larvae were fixed 15 min after feeding, it was found that the spores remained relatively unchanged but that the matrix of the paraspores was dissolved. After dissolution of the paraspore matrix, a meshlike envelope remained which retained the paraspore shape and which was often in contact with the cross-cell portion of the exosporium. The parasporal crystals may be a source of the mosquito larval toxin in this strain of B. sphaericus, but proof will require their isolation from other cellular components.

Journal Article↗
PubMed1980

Localization of a mosquito-larval toxin of Bacillus sphaericus 1593.

Cell-free wall, membrane, and cytoplasmic fractions were prepared from Bacillus sphaericus 1593, which exhibited toxic activity against larvae of the mosquito Culex pipiens var. quinquefasciatus. Breakage of 12- to 14-h cells by sonication or French pressure cell yielded toxic material which could be assayed in a standard mosquito larva bioassay. When sporulating cells of strain 1593 were fractionated, the majority of the toxic activity was localized in the cell wall rather than in the plasma membrane or cytoplasm. The toxin located in the bacterial cell wall was relatively stable, in that activity was unaffected by treatment with trypsin, pronase, CHCl3-CH3OH-water, Triton X-100, 8 M urea (30 min), heat (80 degrees C, 12 min), sonication, refrigeration, lyophilization, or freezing. Activity was destroyed by boiling for 10 min or by 0.01 N NaOH. Only about 1.0% of the activity present in purified cell walls could be recovered by a 2-h extraction with 8 M urea or 3 M guanidine hydrochloride. A comparison of the toxicity of a cell-free cell wall fraction with that of a sample consisting entirely of heat-stable spores indicated that the spore preparation was about 10 times more active.

Animals↗
PubMed1979

Comparative studies of the mosquito-larval toxin of Bacillus sphaericus SSII-1 and 1593.

Two strains of Bacillus sphaericus. SSII-1 and 1593, were bioassayed for toxic activity against second-instar larvae of the mosquito Culex pipiens quinquefasciatus. It was found that strain 1593 developed a level of toxicity 3000 times that of strain SSII-1. Although the toxic activity of B. sphaericus SSII-1 was relatively unchanged throughout growth, an increase in activity of strain 1593 occurred as the bacteria began to sporulate. Strain differences were examined by (i) growth cycle experiments, (ii) bioassays of the toxicity of oligosporogenous mutants, and (iii) manganese limitation experiments. The toxin of strain 1593 was shown to be more stable than that of strain SSII-1. Unlike the spores of strain SSII-1, the spores of B. sphaericus 1593 were found to be highly toxic. Thin sections of SSII-1 or 1593 cells did not reveal the presence of any inclusion body that might be related to toxicity.

Animals↗
PubMed1978

Toxic activity of Bacillus sphaericus SSII-1 for mosquito larvae.

Using larvae of the mosquito Culex pipiens var. quinquefasciatus as a bioassay system, we have verified an earlier proposal that pathogenicity of Bacillus sphaericus SSII-1 is a toxin-mediated rather than an infectious process. Chloroform or ultraviolet-light treatments that decreased the viable count of SSII-1 cells by 4 or 5 logs did not significantly alter the ability of the bacterial cells to kill larvae. Three lines of evidence indicated that toxic activity was not related to sporulation: (i) cells grown in either a complex or a defined medium were toxic at all ages; (ii) when supplemental Mn2+ was excluded from a complex medium, the culture yielded few spores but was of equal toxicity to a culture containing many spores; and (iii) several early blocked oligosporogenous mutants were isolated that had toxic activities comparable to that of the parent. The toxin was shown to be relatively unstable because activity was destroyed by heat and decreased by refrigeration, a freeze-thaw cycle, or two methods of cell breakage. Thin sections of SSII-1 cells did not reveal the presence of any inclusion body that might be related to toxicity.

Animals↗
PubMed1976

Response of Bacillus thuringiensis to bacteriophage CP-51.

Bacteriophage CP-51, a transducing phage of Bacillus cereus was able to replicate on all eight varieties of Bacillus thuringiensis tested. Three general plaque types were observed on each strain although one type predominated on each strain. The plaque size was uniform for each strain regardless of plaque type. The bacterial strain used as source of the phage had no effect on plaque type or size found on any host strain. CP-51 was stable in infected spores of B. thuringiensis var. kurstaki for at least 305 days even though most of the spores had lost refractility. Free phage paricles produced in B. thuringiensis were stable for at least 10 days in broth at 14 degrees C but were very unstable at 4 degrees C.

Bacillus cereus↗
PubMed1975

Metalloprotease from Bacillus thuringiensis.

Bacillus thuringiensis var. kurstaki was shown to produce an extracellular, metal chelator-sensitive protease during the early stages of sporulation. Protease production in nutrient broth was dependent upon supplementation with Mn2+ or Ca2. The addition of Ca24 was required for enzyme stabilization...

Bacillus thuringiensis↗
PubMed1975

Oxygen metabolism of catalase-negative and catalase-positive strains of Lactobacillus plantarum.

Two catalase-negative strains of Lactobacillus plantarum and a strain producing the atypical, nonheme catalase were studied to determine if the ability to produce the atypical catalase conferred any growth advantage upon the producing strain. Both catalase-negative strains grew more rapidly than the catalase-positive strain under aerobic or anaerobic conditions in a glucose-containing, complex medium. Upon exhaustion of glucose from the medium, all three strains continued growth under aerobic but not under anaerobic conditions. The continued aerobic growth was accompanied by production of acetic acid in addition to the lactic acid produced during growth on glucose. Oxygen was taken up by exponential phase-cell suspensions grown on glucose when glucose or glycerol were used as substrates. Cells harvested from glucose-exhausted medium oxidized glucose, glycerol, and pyruvate. Oxygen utilization by a catalase-negative strain increased as did the specific activity of reduced nicotinamide adenine dinucleotide peroxidase during late growth in the glucose-exhausted medium. The catalase-positive strain and the catalase-negative strain tested both possessed low but readily detectable levels of superoxide dismutase throughout growth. The growth responses are discussed in terms of the presence of enzymes which would allow the cells to remove potentially damaging reduction products of O2.

Acetates↗
PubMed1975

Germination of Bacillus cereus endospores: a proposed role for heat shock and nucleosides.

Spores of Bacillus cereus T prepared in a glucose - yeast extract - salts broth germinated in L-alanine or more rapidly in L-alanine plus inosine or adenosine. The nucleosides alone were not germinative. Inosine was shown to produce no pregerminative changes in spores that prepared them for more rapid germination later in L-alanine. Experiments which measured the interaction of nucleosides, heat shock, and D-alanine on germination rates suggested that nucleosides may potentiate L-alanine-induced germination by causing discrimination against D-alanine at the L-alanine binding site(s) in the spore. D-Alanine is germinative when used with inosine probably because of L-alanine formation by alanine racemase. Heat shock, a prerequisite to D-alanine plus inosine-induced germination, may facilitate entry of inosine into the spore in amounts needed to discriminate against D-alanine.

Adenosine↗
PubMed1973

Superoxide dismutase in Bacillus popilliae, a catalaseless aerobe.

Bacillus popilliae, a cytochrome-containing aerobic organism that lacks catalase and peroxidase, was examined for superoxide dismutase activity. The activity was quite high relative to a wide variety of organisms previously surveyed and was induced by oxygen. No correlation could be made between superoxide dismutase activity and the unexplained death of this organism after completion of exponential growth.

Aerobiosis↗
PubMed1972

Sporulation of tricarboxylic acid cycle mutants of Bacillus subtilis.

A mutant of Bacillus subtilis 168 lacking aconitase (EC 4.2.1.3) was found to be blocked at stage 0 or I of sporulation. Although adenosine triphosphate levels, which normally decrease in tricarboxylic acid cycle mutants at the completion of exponential growth, could be maintained at higher levels by feeding metabolizable carbon sources, this did not permit the cells to progress further into the sporulation sequence. When post-exponential-phase cells of mutants blocked in the first half of the tricarboxylic acid cycle were resuspended with an energy source in culture fluid from post-exponential-phase wild-type B. subtilis or Escherichia coli, good sporulation occurred. The spores produced retained the mutant genotype and were heat stable but lost refractility and heat stability several hours after their production.

Acetates↗
PubMed1969

Metabolism of Bacillus thuringiensis in relation to spore and crystal formation.

A general pattern of metabolism was determined for Bacillus thuringiensis grown in a glucose-yeast extract-salts medium. The pattern did not differ significantly from that of B. cereus grown in a similar medium. Acetic acid produced from glucose during exponential growth was further catabolized in the early sporulation phase of growth, at which time the specific activity of aconitate hydratase increased markedly. Fluoroacetate and alpha-picolinate prevented the removal of accumulated acid, and the resulting low pH inhibited spore and crystal synthesis. Neither crystal-related antigens nor insect toxicity was shown by cells whose crystal synthesis was inhibited in this way. alpha-Picolinate prevented the normal increase in specific activity of aconitate hydratase without inhibiting exponential growth. It also inhibited aconitate hydratase in vitro, but only if preincubated with the enzyme. alpha-Picolinate did not inhibit the increase in specific activity of aconitate hydratase or spore and crystal synthesis in a medium buffered near neutrality. Chloramphenicol and actinomycin D inhibited crystal enlargement and sporulation when added to cells in which small crystals had already begun to form. Typical messenger ribonucleic acid-dependent protein synthesis, rather than the type associated with peptide antibiotic synthesis, is thus indicated for the synthesis of crystal peptide subunits.

Bacillus↗
PubMedDate not supplied

Bacillus sphaericus mosquito pathogens in the aquatic environment.

The fate of Bacillus sphaericus spores in the aquatic environment was investigated by suspending spores in dialysis bags in fresh and seawater. Spore viability was lost more rapidly in seawater. Neither B. sphaericus nor B. thuringiensis israelensis (B.t.i.) spores mixed with pond sediment appeared to attach to the sediment. However, rapid decrease in B.t.i. toxicity suggested attachment of parasporal bodies to sediment. B. sphaericus toxin settled more slowly and less completely. B. sphaericus spores fed to larvae of four aquatic invertebrates were mostly eliminated from the animal gut in less than one week. An exception was the cranefly (Tipula abdominalis) where spores persisted in the posterior gut for up to five weeks.

Animals↗
PubMedDate not supplied

Conjugation by mosquito pathogenic strains of Bacillus sphaericus.

A mosquito pathogenic strain of Bacillus sphaericus carried out the conjugal transfer of plasmid pAM beta 1 to other strains of its own and two other serotypes. However, it was unable to conjugate with mosquito pathogens from three other serotypes, with B. sphaericus of other DNA homology groups or with three other species of Bacillus. Conjugation frequency was highest with a strain having an altered surface layer (S layer). Conjugal transfer of pAM beta 1 was not detected in mosquito larval cadavers. B. sphaericus 2362 was unable to mobilize pUB110 for transfer to strains that had served as recipients of pAM beta 1. These observations suggest that it is unlikely that genetically engineered B. sphaericus carrying a recombinant plasmid could pass that plasmid to other bacteria.

Animals↗