Restriction of bacteriophage plaque formation in Streptomyces spp.

Several Streptomyces species that produce restriction endonucleases were characterized for their ability to propagate 10 different broad host range bacteriophages. Each species displayed a different pattern of plaque formation. A restrictionless mutant of S. albus G allowed plaque formation by all 10 phages, whereas the wild-type strain showed plaques with only 2 phages. DNA isolated from three of the phages was analyzed for the presence of restriction sites for Streptomyces species-encoded enzymes, and a very strong correlation was established between the failure to form plaques on Streptomyces species that produced particular restriction enzymes and the presence of the corresponding restriction sites in the phage DNA. Also, the phages that lacked restriction sites in their DNA generally formed plaques on the corresponding restriction endonuclease-producing hosts at high efficiency. The DNAs from the three phages analyzed also generally contained either many or no restriction sites for the Streptomyces species-produced enzymes, suggesting a strong evolutionary trend to either eliminate all or tolerate many restriction sites. The data indicate that restriction plays a major role in host range determination for Streptomyces phages. Analysis of bacteriophage host ranges of many other uncharacterized Streptomyces hosts has identified four relatively nonrestricting hosts, at least two of which may be suitable hosts for gene cloning. The data also suggest that several restriction systems remain to be identified in the genus Streptomyces.     

Association between cutaneous occlusive vascular disease, cigarette smoking, and skin slough after rhytidectomy

This prospective study attempted to determine if nonreversible occlusive vascular changes in the skin contribute to skin slough after rhytidectomy. The dermal microvasculature from 83 consecutive rhytidectomies was evaluated for intimal proliferation and/or hyalin sclerosis. Occlusive vascular disease increased progressively with age in all patients, but smokers and ex-smokers had significantly greater involvement than nonsmokers at any given age (p = 0.03). Severe occlusive vascular disease and skin slough were associated (p = 0.02), and there was a strong trend toward an association between active smoking and skin slough (p = 0.06). Among smokers, there was a significant relationship between skin slough and failure to abstain from smoking postoperatively (p = 0.006). We conclude that with aging, nonreversible occlusive changes develop in the dermal microvasculature. These changes appear to be accelerated by cigarette smoking. Our data, however, show that these nonreversible occlusive vascular changes by themselves do not completely account for the occurrence of skin slough after rhytidectomy.     

Relationship between oxygen and siderophore synthesis inPseudomonas aeruginosa

Pseudomonas aeruginosa strain PAO1, growing in low-iron medium, produces two siderophores, pyochelin and pyoverdin, in massive bursts as the culture shifts from logarithmic phase to stationary phase. Two medium components, oxygen and iron, prolonged the logarithmic phase when they were added to the medium. Oxygen and iron appeared to be in demand during this period because, as heme synthesis increased in response to the low oxygen concentration in the medium, a situation resulting from the high density of bacteria present in the medium during late log phase, the iron content of the bacteria decreased. These phenomena resulted in the production of massive amounts of siderophores late in the log phase to supply iron for the increased heme synthesis.     

Human anticentromere antibodies: Distribution,characterization of antigens,and effect on microtubule organization

Properties of human anticentromere autoantibodies were analyzed. In intact cells or isolated cell fractions, these sera stain the centromeres of mitotic chromosomes and discrete speckles (prekinetochores) in nuclei. Staining is also retained in matrix preparations from nuclei or chromosomes. Immunoprecipitation or immunoblotting demonstrates protein antigens of 14, 20, 23, and 34 kd in HeLa nuclei and chromosomes; immunoprecipitates of nuclei also contain a protein of 15.5 kd. Matrix preparations contain only the 20, 23, and 34 kd species. Absorption of the anticentromere serum with any one of the four nuclear antigens immobilized on nitrocellulose is sufficient to eliminate centromere staining. Using a lysed cell model for microtubule nucleation, anticentromere sera are shown to inhibit specifically the organization of microtubules at the kinetochore.     

Mutations in the uncE gene affecting assembly of the c-subunit of the adenosine triphosphatase of Escherichia coli.

The amino acid substitutions in the mutant c-subunits of Escherichia coli F1F0-ATPase coded for by the uncE429, uncE408 and uncE463 alleles affect the incorporation of these proteins into the cell membrane. The DNA sequence of the uncE429 allele differed from normal in that a G leads to A base change occurred at nucleotide 68 of the uncE gene, resulting in glycine being replaced by aspartic acid at position 23 in the c-subunit. The uncE408 and uncE463 mutant DNA sequences were identical and differed from normal in that a C leads to T base change occurred at nucleotide 91 of the uncE gene, resulting in leucine being replaced by phenylalanine at position 31 in the c-subunit. An increased gene dosage of the uncE408 or uncE463 alleles resulted in the incorporation into the membranes of the mutant c-subunits. The results are discussed in terms of the 'Helical Hairpin Hypothesis' of Engelman & Steitz [(1981) Cell 23,411-422].     

Thecal ultrastructure ofScrippsiella faeroense

Summary The thecal ultrastructure ofScrippsiella faeroense (Paulsen) Balech and Oliveira Soares as seen in the electron microscope is described. Additional structural detail of the thecal plate surface, plate connections, and the apical pore, is revealed.     

Selection for High Mutation Rates in Chemostats

Complementation and polarity suppression data are interpreted in terms of the genetic structure of the maltose B region. It is proposed that this region comprises two divergent operons. One operon includes malK, a cistron involved in maltose permeation, and lamB the only known cistron specifically involved in lambda receptor synthesis. The other operon includes malJ(1) and malJ(2) which are most probably two different cistrons, both involved in maltose permeation*. It is further assumed that expression of the two operons is controlled by malT, the positive regulatory gene of the maltose system, located in the malA region. The target(s) for the action of the malT product is (are) most likely to be located between malJ(1) and malK. There is an indication that the two operons might overlap in the region of their promoters. The structure of such an overlap as well as the possible function of the products of the different cistrons in malB are briefly discussed.     

Carnitine and trimethylaminobutyrate synthesis in rat tissues (Short Communication)

Liver and testis slices convert 6-N-trimethyl-lysine into 4-N-trimethylaminobutyrate and carnitine. Adipose, skeletal muscle, heart, or kidney tissues metabolize trimethyl-lysine into trimethylaminobutyrate but not into carnitine. Trimethylaminobutyrate hydroxylation, forming carnitine, occurs in liver and to a minor degree in testis. Liver is the primary site of carnitine biosynthesis in the rat.