Use of nalidixic acid for constructing the replication map of theMycobacterium phlei chromosome

Nalidixic acid was used for describing more accurately the terminal replication region of theMycobacterium phlei chromosome. Cell division in synchronized cultures was not sensitive to this acid any more between 185–190 min,i.e. about 10 min after replication of theser gene the last of 24 genes of the replication map described so far. The replication of the chromosome was controlled by determining the position of thebac gene. Microscopic studies in phase contrast of the cells that were subjected for long time periods to nalidixic acid treatment at a bactericidal concentration showed elongated cells. The electron-microscopic observation showed that a portion of the population influenced by nalidixic acid lyzes, whereas other cells remain intact and resemble control cells.     

RHG-band polymorphism of the short arms of human acrocentric chromosomes and relationship of variants to satellite associations

Summary The extent of RHG-band variation of short arms of human acrocentric chromosomes was investigated in a group of 100 subjects by visually comparing the variants with the size of reference bands 7p22, 21q22 and 11q13. Marked differences were found among the chromosomes in the distribution of variants; the largest mean size of RHG-band was associated with chromosome 21, whereas the variants of chromosome 22 had the smallest band size. The study further showed that the involvement of acrocentric chromosomes in satellite association did not depend upon the size of RHG-band variants.     

Curing effect of clorobiocin on Escherichia coli plasmids

Summary Clorobiocin, an inhibitor of the gyrB subunit of DNA gyrase, was used for the curing of some Escherichia coli plasmids. Of the plasmids studied, ampicillin resistant R28K and a miniplasmid derived from R1 drd-19 were effectively eliminated. We also succeeded in eliminating the ColA factor from E. coli strain B834 (pBS103), which was resistant to the effect of currently used curing agents. Although a derivative of ColE1-pBR322 was effectively cured by clorobiocin, the ColE1-plasmid was resistant to its effect. The ColV plasmid determining virulence was effectively eliminated.     

Acetylcoenzyme A and Acetylcholine in Slices of Rat Caudate Nuclei Incubated with (-)-Hydroxycitrate, Citrate, and EGTA

Abstract: The effects of (-)-hydroxycitrate (OHC) and citrate on the concentration of acetylcoenzyme A (acetyl-CoA) and acetylcholine (ACh) in the tissue and on the release of ACh into the medium were investigated in experiments on slices of rat caudate nuclei incubated in media with 6.2 or 31.2 m M K⁺, 0 or 2.5 mM Ca²⁺, and 0, 1, or 10 m M EGTA. OHC diminished the concentration of acetyl-CoA in the slices under all conditions used: in experiments with 2.5 m M OHC, the concentration of acetyl-CoA was lowered by 25-38%. Citrate, in contrast, had no effect on the level of acetyl-CoA in the tissue. Although both OHC and citrate lowered the concentration of ACh in the slices during incubations with 6.2 m M K⁺ and 1 m M EGTA, they had different effects on the content of ACh during incubations in the presence of Ca²⁺. The concentration of ACh in the slices was increased by citrate during incubations with 2.5 mM Ca²⁺ and 31.2 or 6.2 m M K⁺, but it was lowered or unchanged by OHC under the same conditions. The release of ACh into the medium was lowered or unchanged by OHC and lowered, unchanged, or increased by citrate. It is concluded that most effects of OHC on the metabolism of ACh can be explained by the inhibition of ATP-citrate lyase; with glucose as the main metabolic substrate, ATP-citrate lyase appears to provide about one-third of the acetyl-CoA used for the synthesis of ACh. Experiments with citrate indicate that an increased supply of citrate may increase the synthesis of ACh. The inhibitory effect of citrate on the synthesis of ACh, observed during incubations without Ca⁺², is interpreted to be a consequence of the chelation of intracellular Ca²⁺; this interpretation is supported by the observation of a similar effect caused by 10 m M EGTA.     

Pkg2, a Novel Transmembrane Protein Ser/Thr Kinase of Streptomyces granaticolor

A 4.2-kb SphI-BamHI fragment of chromosomal DNA from Streptomyces granaticolor was cloned and shown to encode a protein with significant sequence similarity to the eukaryotic protein serine/threonine kinases. It consists of 701 amino acids and in the N-terminal part contains all conserved catalytic domains of protein kinases. The C-terminal domain of Pkg2 contains seven tandem repeats of 11 or 12 amino acids with similarity to the tryptophan-docking motif known to stabilize a symmetrical three-dimensional structure called a propeller structure. The pkg2 gene was overexpressed in Escherichia coli, and the gene product (Pkg2) has been found to be autophosphorylated at serine and threonine residues. The N- and C-terminal parts of Pkg2 are separated with a hydrophobic stretch of 21 amino acids which translocated a PhoA fusion protein into the periplasm. Thus, Pkg2 is the first transmembrane protein serine/threonine kinase described for streptomycetes. Replacement of the pkg2 gene by the spectinomycin resistance gene resulted in changes in the morphology of aerial hyphae.     

Stomatal Morphology during Acclimatization of Tobacco Plantlets to ex vitro Conditions

Image analysis was used in studying stomatal morphology during acclimatization of tobacco plantlets to ex vitro conditions, 45 d after transfer leaf area was 15 times, and total number of stomata per leaf four times increased. During acclimatization stomatal density was decreased considerably on both leaf sides, and was compensated by an increase in stomatal sizes, e.g., in stomatal length and in stomatal area (both guard cells and pore). Elongation of stomata was increased indicating that the originally circular stomata of in vitro plantlets were changed into elliptical ones in ex vitro acclimatized plants. This revised version was published online in June 2006 with corrections to the Cover Date.