Michio Matsuhashi

Chapter 4 Utilization of lipid-linked precursors and the formation of peptidoglycan in the process of cell growth and division: membrane enzymes involved in the final steps of peptidoglycan synthesis and the mechanism of their regulation

Publisher Summary This chapter discusses the utilization of lipid-linked precursors and the formation of peptidoglycan in the process of cell growth and division. Peptidoglycans are basic constituents of bacterial cell walls. Their structure is common to most eubacteria. However, there are certain divergences among the peptidoglycans characterizing various species of bacteria. Moreover, they are also thought to differ according to the topology of the cell. The enzymes and enzymatic reactions involved in their biogenesis and the mechanism of their regulation are therefore diverse to a certain extent among various species and stages of their cell cycles. The pathway consists of: (1) formation of UDP-MurNAc-pentapeptide through a sequence of cytoplasmic enzyme reactions; (2) transfer of MurNAc-pentapeptide to undecaprenyl-phosphate on the membrane and addition of GlcNAc to form undecaprenyl-pyrophosphate-linked disaccharide-pentapeptide; and (3) transfer of disaccharide-pentapeptide residues to form peptidoglycan. Early experiments on peptidoglycan synthesis were conducted without sufficient attention to the genetic background of the biosynthesis.

Description of Bacillus carboniphilus sp. nov.

We observed activation of growth with six aerobic spore-forming isolates on an otherwise nonpermissive medium when a carbon material, such as graphite or activated charcoal, was added to the medium (Bacto Antibiotic Medium 3). On the basis of the phenotypic characteristics and physiological and biochemical properties of these organisms and DNA homology data we concluded that they belong to a new Bacillus species, which is designated Bacillus carboniphilus. Strain Kasumi 6 (= JCM 9731) is the type strain of this new species.

A novel life cycle arising from leaf segments in plants regenerated from horseradish hairy roots

SummaryHorseradish (Armoracia rusticana) hairy root clones were established from hairy roots which were transformed with the Ri plasmid in Agrobacterium rhizogenes 15834. The transformed plants, which were regenerated from hairy root clones, had thicker roots with extensive lateral branches and thicker stems, and grew faster compared with non-transformed horseradish plants. Small sections of leaves of the transformed plants generated adventitious roots in phytohormone-free G (modified Gamborgs) medium. Root proliferation was followed by adventitious shoot formation and plant regeneration. Approximately twenty plants were regenerated per square centimeter of leaf. The transformed plants were easily transferable from sterile conditions to soil. When leaf segments of the transformed plants were cultured in a liquid fertilizer under non-sterile conditions, adventitious roots were generated at the cut ends of the leaves. Adventitious shoots were generated at the boundary between the leaf and the adventitious roots and developed into complete plants. This novel life cycle arising from leaf segments is a unique property of the transformed plants derived from hairy root clones.

β-Lactams and Other Innovative New Approaches for Controlling Bacterial Populations

β-lactam antibiotics, with a history far longer than most people imagine, date back to antiquity in Greece, China and other countries [1]. They were first documented with scientific precision by Alexander Fleming in 1929 [2], and were developed to the stage of large-scale production for clinical use by H.W. Florey and his collaborators [3].

From Carbon to Biosonics

Several studies showing the definite growth-enhancing or promoting effect of carbon material upon certain bacteria have been reported. Charcoal and graphite added to solidified or liquid culture media enhanced the growth of Gonococcus and Meningococcus [1], Legionella pneumophila [2], and Haemophilus pertussis [3] ; and of several strains of Bacillus carboniphilus [4–6] and Bacillus stearothermophilus [6] under a non-permissive stress condition. It has been proposed that activated charcoal detoxifies peroxide and various free radicals of oxygen in culture media, resulting in the enhancement of the growth of Legionella [7].

Further Studies onrodAMutant: a Round Morphological Mutant ofEscherichia coliK-12 with Wild-Type

Escherichia coli rodA mutant AOS151 grows as round cells at 30 and 42°C (H. Matsuzawa, K. Hayakawa, T. Sato, and K. Imahori, J. Bacteriol., 115, 436–442 (1973)). The mutant was found to be resistant to mecillinam at both temperatures. lip+ transductants were prepared by Pl phage transduction via strain AOS151, the cotransduction frequency of round morphology (Rod−) at 42°C with the lip gene being about 90%. At 42°C all 54 Rod− transductants tested were resistant to mecillinam. At 30°C all but two of these Rod− (at 42°C)-type transductants were rod-shaped, and all were sensitive to mecillinam; the two strains grew as ovoid cells. The original rodA mutant AOS151 probably involves an additional mutation(s), that expresses the round cell shape at lower temperature, whereas the rodA51 mutation alone seems to result in temperature-sensitive expression of round cell morphology and mecillinam resistance. rodA mutant cells cultured at either 30 or 42°C had wild-type penicillin-binding protein 2, judging from penic...