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Biomedical subjects

M R Loeb

Publications and source records attributed to M R Loeb.

24 records · Page 2Linked to original sources
PubMed1980

Outer membrane protein composition in disease isolates of Haemophilus influenzae: pathogenic and epidemiological implications.

The outer membrane protein composition of 50 disease isolates of Haemophilus influenzae has been determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All strains, including 28 strains of serotype b, one strain each of serotypes a, c, d, e, and f, and 17 untypable strains, had an outer membrane protein composition typical of gram-negative bacteria, i.e., these membranes contained two to three dozen proteins with four to six proteins accounting for most of their protein content. Variation in the mobility of these major outer membrane proteins from strain to strain was common but not universal; the observed patterns provided useful data and new insight into the epidemiology of type b disease. The basic findings can be summarized as follows: (i) All 50 strains possessed three proteins (one minor and two major) each having identical mobilities. The other proteins, both major and minor, varied in mobility. (ii) All type b strains possessed a fourth (major) protein of identical mobility. (iii) The 28 type b strains, on the basis of the mobility of the six major outer membrane proteins, could be divided into eight subtypes. Of all the other strains examined, both typable and untypable, only the serotype a strain belonged to one of these subtypes. (iv) The untypable strains showed considerable variation in the mobilities of their major outer membrane proteins. Of these 17 strains, 13 had an additional major outer membrane protein not present in encapsulated strains. (v) The outer membrane protein composition of a single strain remained unchanged after many passages on solid media, but varied with the growth phase. (vi) The outer membrane protein composition of isolates obtained from nine patients during an epidemic of type b meningitis varied, indicating that a single strain was not responsible for the epidemic. At least five different strains were responsible for these nine cases. (vii) Identical outer membrane protein compositions were observed in the following: in a type b strain and a mutant of this strain deficient in capsule production, indicating that the level of capsule synthesis is not obviously related to outer membrane protein composition; in type b strains isolated from different anatomic sites of patients acutely ill with meningitis, indicating that the strain associated with bacteremia is the same as that isolated from the cerebrospinal fluid; in type b strains isolated from siblings who contracted meningitis at about the same time, indicating infection with the same strain; and in type b strains isolated from the initial and repeat infection of a single patient, suggesting that reinfection was due to the same strain.

Bacterial Proteins↗
PubMed1979

Effect of growth medium on the relative polypeptide composition of cellular outer membrane and released outer membrane material in Escherichia coli.

When ratios of the major polypeptides of the outer membrane isolated from cells of Escherichia coli B grown in minimal medium containing either a single amino acid or several amino acids were compared, no difference was observed. However, the ratio of these polypeptides in outer membrane material released into the medium during logarithmic phase growth on these two media was markedly different.

Amino Acids↗
PubMed1978

Lipopolysaccharide interferes with the staining of lipoprotein on polyacrylamide gels.

After electrophoresis of total membrane preparations of Escherichia coli B on sodium dodecyl sulfate polyacrylamide gels, and subsequent staining with Coomassie Brilliant blue, a band corresponding to the Braun lipoprotein fails to appear. This is in contrast to similar preparations of E. coli K-12 which do display the lipoprotein upon staining. Experiments described below indicate that failure to observe this protein in E. coli B is due to interference in the staining reaction by the lipopolysaccharide present in the membrane preparations.

Bacterial Proteins↗
PubMed1978

Release of a special fraction of the outer membrane from both growing and phage T4-infected Escherichia coli B.

Growing Escherichia coli release envelope material into the medium. Upon infection with T4 phage increased amounts of this material are released and at a greater rate. In order to determine whether both inner and outer membranes are present in this material, and whether the material released by growing cells differs from that released by infected cells, we have examined the protein composition of envelope released by growing and T4-infected E. coli B. Our results show: (a) the protein composition of envelope released from growing or infected cells is similar, (b) the proteins present are representative of the outer membrane, (c) the major outer membrane protein of E. coli B, protein II, is deficient in the released material. We therefore conclude that the envelope material released from growing or infected E. coli represents a special fraction of the outer membrane. This finding is discussed in relation to outer membrane structure and function. In addition, data are presented on the differing outer membrane protein composition of substrains of E. coli B obtained from different laboratories.

Bacterial Proteins↗
PubMed1974

Bacteriophage T4-mediated release of envelope components from Escherichia coli.

When Escherichia coli B, labeled by prior growth in (14)C-glucose, are infected with T4 phage there is a rapid release of (14)C-nondialyzable material into the medium. About half of this material is derived from the cell envelope as evidenced by its content of phospholipid and lipopolysaccharide and its buoyant density upon isopycnic ultracentrifugation of 1.19 g/cm(3). It is similar in its gross chemical and physical properties to envelope material released at a lower rate from growing uninfected cells or from cells whose protein synthesis is inhibited by chloramphenicol (22). The rate of release of this envelope material at a multiplicity of infection (MOI) of 10 is greatest in the first minute after infection, and release is completed by 4 min. The rate of its release, as a function of MOI at 2 min after infection, is greatest at low MOI (e.g., MOI 2 and 4); in addition, the release does not continue above MOI 30. The main conclusion derived from the data is that phage, as part of the process of adsorption and injection of DNA, cause an increased release of envelope substance from the cells. With the assumption that all of the envelope material released is derived from the outer envelope, it is estimated that uninfected cells release 20 to 30% of their outer envelope per hour, whereas infected cells release 30% in 2 min at MOI 30. Further, because release does not continue at high MOI, this phenomenon is not considered to be a direct cause of lysis from without. Data are also presented on the amounts of other non-dialyzable (14)C-components released and on the differences in the kinetics of release from chloramphenicol-treated cells compared to phage-infected cells. To avoid the possibility that the release is due to phage lysozyme which is an adventitious "contaminant" of wild-type phage, a phage mutant (T4BeG59s) devoid of this enzyme was used in these experiments.

Adsorption↗