Biomedical subjects

V L Clark

Publications and source records attributed to V L Clark.

58 records · Page 4Linked to original sources

PubMed1972

Changes in free amino acid production and intracellular amino acid pools of Bacillus licheniformis as a function of culture age and growth media.

Changes in the endogenous intracellular amino acid pool and total free amino acid production in Bacillus licheniformis grown in minimal media were investigated. The total intracellular pool increased during exponential growth and then decreased rapidly after the end of growth. Most of the amino acids were present at low concentrations, but glutamate and alanine comprised 60 to 90% of the total intracellular free amino acid at most times during the growth cycle. It was concluded that, in addition to providing monomers for protein synthesis, the intracellular amino acid pool may be maintained for the storage of energy-providing metabolic intermediates and possibly as a balance to the ionic strength of the medium. The total free amino acid production by the cell was found to be dependent upon the composition of the salts medium as well as the culture age under conditions in which the carbon and nitrogen sources were the same. A 10-fold increase in extracellular amino acid was observed as the cells changed from vegetative to sporulation metabolism, mostly due to the extrusion of intracellular amino acid. The impact of this increase upon amino acid uptake and pulse-labeling studies using unwashed cells is discussed.

Alanine↗

PubMedDate not supplied

Inhibition of active transport and macromolecular synthesis by pyocin 103 in Neisseria gonorrhoeae.

The mechanism of inhibition of Neisseria gonorrhoeae by pyocin 103 was examined. Pyocin 103 decreases the viability of N. gonorrhoeae immediately after its addition to logarithmically growing cells by single-hit kinetics. This inhibition was paralleled by an immediate cessation of protein synthesis, RNA synthesis, and active transport. From the data presented, it is likely that pyocin kills N. gonorrhoeae in the same manner that it kills Pseudomonas aeruginosa, i.e., by interfering with energy metabolism.

Bacterial Proteins↗

PubMedDate not supplied

Construction and characterization of chimeric beta-lactamase plasmids of Neisseria gonorrhoeae with altered ability to be mobilized during conjugation.

A series of chimeric plasmids derived from the transfer factor, beta-lactamase-encoding R factor, and cryptic plasmid of Neisseria gonorrhoeae was constructed. Two of these plasmids, each lacking a 1.9-kilobase-pair (kb) HinfI fragment, could not be mobilized by the 40-kb gonococcal transfer factor to recipient strains of N. gonorrhoeae or Escherichia coli during conjugation. The proteins encoded by both the naturally occurring and chimeric plasmids were examined with an E. coli cell-free transcription-translation system and in E. coli maxicells. Six plasmid-specific proteins were identified when DNA from a naturally occurring 7.1-kb R factor was used as template. A small protein (16,000 daltons), which is apparently not encoded by the two plasmids lacking the 1.9-kb HinfI fragment, appears to be necessary for plasmid transfer during conjugation.

Bacterial Proteins↗

PubMedDate not supplied

The heat shock response of type 1 and type 4 gonococci.

A heat shock response, characterized by the elevated expression of certain proteins in response to a shift to a higher temperature, has been observed in both eukaryotic and prokaryotic organisms. We have characterized the heat shock response of the pathogenic organism N. gonorrhoeae, colony types 1 and 4. Following a shift up in temperature from 37 C to 43 C, two-dimensional gel electrophoretic analysis was used to identify 19 heat shock proteins in Type 1 and 37 heat shock proteins in Type 4 gonococci. One heat shock protein was found only in Type 1, 19 were common to both Type 1 and Type 4, and 19 were found only in Type 4 gonococci. Most heat shock proteins were found in the cytoplasm, some in the cytoplasmic membrane, and none could be detected in the outer membrane. Pulse-chase experiments revealed that heat shock proteins were very stable.

Autoradiography↗