- Volume 32, Issue 1, 1963

SUMMARY: Leprosy bacilli have not been cultivated with certainty in any cell-free medium, but the medium now described consistently supported considerable elongation of the organisms of murine leprosy (Mycobacterium lepraemurium), though without evidence of multiplication. The mean length of the bacilli doubled in about the generation time obtaining in host cells (7-14 days) and quadrupled before the bacilli became degenerate after about 2 months. The obligate acidity and other factors concerned in this growth were investigated, and are discussed in relation to the problem of the extracellular cultivation of leprosy bacilli.

Non-capsulated variants of Bacillus anthracis have been said not to revert to the capsulated state. However, in the present work, capsulated revertants were isolated from about half the non-capsulated strains tested either by exposure to phage Wα, which attacks only non-capsulated organisms, or by passage in mice.

The properties of four Lactobacillus casei phages and eleven L. fermenti phages are presented. Most of these phages are species specific; some have a limited intraspecies action. The two groups of phages are serologically distinct, but the members of each group are related serologically. All the phages have slow adsorption rates. The L. casei phages are citrate insensitive, while some of the L. fermenti phages are citrate sensitive. The L. fermenti phages have shorter latent periods than the L. casei phages and this correlates directly with the generation times of their hosts. The phages are large and have a tadpole appearance.

A Flavobacterium sp. isolated from soil and grown in media containing 4-(2,4-dichlorophenoxy) butyric acid (4-(2,4-DB)) metabolized 2,4-dichloro-phenol and 4-chlorocatechol without a preliminary period of induction. The initial oxidation of 4-(2,4-DB) was rapid, but the rate declined to a value equivalent to that observed for butyric and crotonic acid oxidation. The bacterium produced 2,4-dichlorophenol, 4-chlorocatechol and butyric and crotonic acids when grown in the presence of 4-(2,4-DB). It is proposed that the initial step in 4-(2,4-DB) oxidation involves a cleavage of the ether linkage rather than β-oxidation of the aliphatic moiety.

SUMMARY: The development of resistance to ampicillin (aminophenylacetamidopenicillanic acid) and penicillin G was investigated by selecting resistant variants of strains of Escherichia coli. Resistance occurred in stepwise manner. The parent strains contained minute amounts of penicillinase and production of the enzyme by resistant variants increased in relation to increase in resistance. Evidence was obtained that production of penicillinase was responsible for this increase in resistance. By using resistant variants and naturally occurring ampicillin-resistant organisms, it was found that production of only small amounts of penicillinase was sufficient to confer a high degree of resistance to the Gram-negative bacteria examined. In contrast, Gram-positive bacteria required much greater quantities of penicillinase for high grade resistance. It is suggested that an important reason for this difference is the complex lipid-containing cell wall of Gram-negative bacteria, which slows penetration by penicillin and enables small amounts of penicillinase to protect the cell. The penicillinase of all the Gram-negative organisms investigated was found to be a β-lactamase and to be more active against penicillin G than against ampicillin. This provides one explanation for the greater activity of ampicillin against Gram-negative bacteria.

SUMMARY: Several steroids closely related structurally to cholesterol were tested for growth-promoting activity for a strain of Mycoplasma mycoides (V5) and a Mycoplasma sp. isolated from a goat (gy). Cholestanol and latho-sterol promoted growth of both strains. Cholestenone, cholest-5-en-3-one, 7-dehydrocholesterol and progesterone inhibited cholesterol-promoted growth; cholestanone was almost inactive either as growth promotor or as growth inhibitor. Cholesterol amounted to 4–5% of the dry weight of the water-washed organisms, or about 20% of the total lipids, of either strain grown in the presence of cholesterol. Cholesterol esters or transformations to other steroids were not detected in lipid extracts of the v5 strain grown in the presence of cholesterol-4-14C. The gy strain was grown in the presence of cholesterol-4-14C of known specific activity, the lipid extract diluted with a known amount of unlabelled cholesterol, and cholesterol isolated and purified. Its specific activity was very close to the value expected if no sterol transformations had occurred. When grown in the presence of cholestanol, the gy strain incorporated this sterol without desaturation.

SUMMARY: Escherichia coli strain 26-26 (a mutant requiring lysine for growth) releases into the medium diaminopimelic acid, lipomucoprotein and nucleotides, including flavins, when grown with suboptimal concentrations of lysine. Cytidine diphosphate glycerol, cytidine diphosphate ribitol and a uridine-linked mucopeptide containing n-acetylmuramic acid, glutamic acid, mesodiaminopimelic acid and alanine were identified among the nucleotides extracted from the medium. Similar uridine diphosphate-linked mucopeptides were isolated from extracts made from bacteria at various stages of growth. In addition, uridine diphosphate-linked mucopeptides were isolated from bacterial extracts which were found to contain muramic acid and lysine but no diaminopimelic acid. The possible role of these compounds as precursors of cell wall structures is discussed.

SUMMARY: The formation of catalase activity by an Arthrobacter strain jg-9 is dependent upon the addition of exogenous haemin, or the iron-containing growth factor ferrichrome. The iron-containing antibiotic ferrimycin A inhibited the synthesis of catalase in bacterial suspensions supplemented with ferrichrome, but did not measurably alter catalase formation in suspensions supplemented with haemin. This suggests that ferrichrome is necessary for haemin (catalase) synthesis, and that ferrimycin A acts by blocking this step. Cell-free extracts of Rhodopseudomonas spheroides were able to synthesize haemin when incubated with an oxidizable substrate, protoporphyrin IX and iron supplied as ferrichrome.

SUMMARY: The non-competitive inhibitors fluoroacetate and arsenite inhibited sporulation and respiration of Venturia inaequalis (Cke.) Wint. to a greater extent than malonate. They also restricted growth. o-Coumaric acid acted similarly to the non-competitive inhibitors but, while not inhibiting growth, it caused changes in the colour of the mycelium, suggesting an altered metabolism. Arsenite increased α-ketoglutarate in the medium and to some extent pyruvate, while o-coumaric acid produced only a slight increase in the concentration of pyruvate. No detectable amounts of succinic acid resulted from the presence of malonate. Injection of o-coumaric acid into scab-infected apple shoots decreased the incidence of disease; malonate had the opposite effect and was strongly phytotoxic.

SUMMARY: The negative staining technique was used to study the morphology of actinophage Φ17 which infects Streptomyces chrysomallus strain s17. It was found that the particle does not possess the characteristic tail of the bacteriophages, and that its capsid is built of distinct subunits.

SUMMARY: Isolates from seven virus stocks called tobacco necrosis were serologically related, but fell into two groups (serotypes) showing widely different degrees of serological relationship. Serotype A contained the five closely related strains a, b, c (Dutch cucumber necrosis virus), f and s (bean stipple-streak virus); and serotype D strains d and e. Strains a and f, isolated in Britain and the U.S.A. respectively, are possibly identical, but the others could be distinguished by the kinds of lesions caused in French bean, and c by the symptoms it causes in young cucumber plants. The virus particles of all strains were hexagonal in outline and of the same width. They had the same absorption spectrum and sedimentation constants, and all except strain b crystallized into rhombic plates. Only strain d failed to aid the multiplication of the satellite virus. It is proposed to restrict the name tobacco necrosis to viruses serologicaly related to what seems the commonest strain, namely, a.

SUMMARY: The immunofluorescent method was applied to a strain of Trypanosoma brucei and of Trypanosoma vivax by using the direct antibody technique. Conjugated antibodies to the soluble antigens of trypanosomes reacted specifically with the homologous species only; antibodies to the bound antigens reacted with both species.