Biomedical subjects

D V Lim

Publications and source records attributed to D V Lim.

23 records · Page 2Linked to original sources

PubMed1978

Differences in susceptibilities of virulent strains and avirulent strains of Neisseria gonorrhoeae to antimicrobial agents.

Virulent cells (T1 colony type) and avirulent cells (T4 colony type) of Neisseria gonorrhoeae were grown in a defined liquid medium in the presence of different antimicrobial agents. Bacteria of T1 colony type were found to be more resistant than bacteria of T4 colony type to the inhibitory effects of specific concentrations of ampicillin (0.50 mug/ml) and penicillin (0.01 mug/ml). Bacteria of T4 colony type, however, were found to be more resistant to the effects of chloramphenicol (0.40 mug/ml), erythromycin (0.10 mug/ml), spectinomycin (10.00 mug/ml), and tetracycline (0.30 mug/ml). The differences in susceptibilities of these bacteria to the antibiotics investigated were not due to differences in growth rate or to differences in permeability. The data suggest that virulent gonococci and avirulent gonococci have unique properties that affect their susceptibilities to certain antimicrobial agents.

Anti-Bacterial Agents↗

PubMed1977

Radiolabeling of and macromolecular syntheses in Neisseria gonorrhoeae types 1 and 4.

Type 1 and type 4 cells of Neisseria gonorrhoeae were grown in a liquid medium that maintained colony type for several hours. Organisms from both types of colonies incorporated labeled glucose, as well as nucleic acid and protein precursors, into specific cellular fractions during growth in the medium. Ribonucleic acid and protein were synthesized actively by the bacteria, with incorporation of label chased by the addition of unlabeled precursors. The method can be used to label type 1 and type 4 cells of gonococci with specific isotopes for studies of metabolic and biochemical changes.

Adenine↗

PubMed1977

Biosynthesis of prodigiosin by non-proliferating wild-type Serratia marcescens and mutants deficient in catabolism of alanine, histidine, and proline.

Mutants of Serratia marcescens Nima, designated as Aut, Hut, or Put, did not utilize L-alanine, L-histidine, or L-proline, respectively, as a sole carbon source but did utilize other amino acids or glycerol as carbon sources. The bacteria were permeable to alanine, histidine, and proline but lacked the enzymes responsible for degradation of these amino acids. The Aut mutant contained no L-alanine dehydrogenase activity, whereas the Hut and Put mutants contained only 7 and 4% of the histidase and proline oxidase activities, respectively, found in the wild-type strain. Rates of oxygen uptake and protein synthesis were significantly lower when the mutants were incubated in the presence of amino acids they could not degrade. Studies of L-[14C]alanine, L-[14C]histidine, and L-[14C]proline incorporation into prodigiosin synthesized by these mutants and the wild-type strain revealed that proline was incorporated intact, whereas all of alanine except the carboxyl group was incorporated into the pigment molecule. Histidine did not enter prodigiosin directly. These data suggested that the presence of unique biosynthetic pathways, independent of primary metabolism, leads to formation of prodigiosin from specific amino acids.

Alanine↗

PubMed1976

Macromolecular syntheses during biosynthesis of prodigiosin by Serratia marcescens.

Amino acids that were utilized as sole sources of carbon and nitrogen for growth of Serratia marcescens Nima resulted in biosynthesis of prodigiosin in non-proliferating bacteria. Addition of alanine, proline, or histidine to non-proliferating cells incubated at 27 C increased the rate of protein synthesis and also caused biosynthesis of prodigiosin. No increase in the rate of protein synthesis was observed upon the addition of amino acids that did not stimulate prodigiosin biosynthesis. Increased rates of synthesis of ribonucleic acid (RNA) and of deoxyribonucleic acid (DNA) (a small amount) also occurred after addition of amino acids that resulted in biosynthesis of prodigiosin. After incubation of 24 h, the total amount of protein in suspensions of bacteria to which alanine or proline was added increased 67 and 98%, respectively. Total amounts of DNA and of RNA also increased before synthesis of prodigiosin. The amounts of these macromolecules did not increase after addition of amino acids that did not induce biosynthesis of progidiosin. However, macromolecular synthesis was not related only to prodigiosin biosynthesis because the rates of DNA, RNA, and protein synthesis also increased in suspensions of bacteria incubated with proline at 39 C, at which temperature no prodigiosin was synthesized. The quantities of DNA, RNA, and protein synthesized were lower in non-proliferating cells than in growing cells. The data indicated that amino acids causing biosynthesis of prodigiosin in non-proliferating cells must be metabolized and serve as sources of carbon and of nitrogen for synthesis of macromolecules and intermediates. Prodigiosin was synthesized secondarily to these primary metabolic events.

Amino Acids↗

PubMed1976

Incorporation of proline into prodigiosin by a Put mutant of Serratia marcesens.

A Put mutant of Serratia marcescens, deficient in proline oxidase and therefore unable to degrade proline, was used to assay for an enzymatic reaction responsible for incorporation of proline into prodigiosin. The reaction had a pH optimum of 7.5 and a Km of 1.1 X 10(-4) M at 27 C. At temperatures above 27 C, the velocity of the reaction decreased with increasing temperature and little activity was detected at 42 C. Activity of the enzyme was directly proportional to the quantity of pigment formed and was inhibited by thioproline, a substrate analog. These data suggested the presence of a unique and specific enzyme in the biosynthetic pathway for prodigiosin.

Alanine↗