- Volume 45, Issue 1, 1966

SUMMARY: Of 103 species of fungi exposed to 10 atmospheres (atm.) pressure of oxygen at 25° for 7 days 52 resumed growth after treatment. Of these, 22 recovered from a similar treatment for 14 days. On resumption of growth, growth rates were the same as those of untreated colonies, after a lag period between decompression and recovery. The lag period varied with species, length of exposure, inoculum source, and in some cases between replicates of a species. More detailed investigation of the reaction of Fusarium solani, Rhizopus arrhizus, Mucor racemosus and M. plumbeus showed that generally the lag periods increased with increasing exposure times, that their extinction points (i.e. the exposure which killed all replicates) varied, and that at exposures approaching the extinction point there was selective survival either of spores or of strains in the latter three fungi.

SUMMARY: A numerical Adansonian analysis has been performed on the results of a wide range of biochemical and physiological characters of organisms at present classified in the genera Corynebacterium, Mycobacterium, Nocardia, Arthrobacter and Jensenia. The results show that some of the organisms need to be reclassified. Corynebacterium ulcerans could be considered as another type of C. diphtheriae, and C. pyogenes and C. haemolyticum have little similarity to any of the other corynebacteria. Corynebacterium equi and Jensenia canicruria appear to be closely related to the mycobacteria examined. The plant pathogens C. rathayi, C. betae and C. michiganense seem to be distinct from most of the animal parasites in this genus. The mycobacteria, nocardia and most of the corynebacteria from animal sources form one large group at the 51% similarity level. Acid-fastness does not seem to be a good criterion for separating the genus Corynebacterium from the genus Mycobacterium, some of the corynebacteria showed varying degrees of acid-fastness.

SUMMARY: Some chemical changes which took place in the mycelium of Aspergillus flavus during autolysis were studied. A. flavus underwent a ‘neutral autolysis’ in which a decrease of 73.9% in mycelial dry weight occurred. Glucose, xylose, maltose and mannitol were found in autolysing mycelium of A. flavus. The loss of free glucose amounted to 10 mg./flask during the whole period of autolysis. Xylose was decreased to half its initial content by the third day of autolysis and then disappeared by the ninth day, whereas maltose decreased at the beginning and then remained constant from the eighty-first to the hundred and eleventh day of incubation. Eighty-nine per cent of the initial amount of mannitol was lost during the first 9 days of autolysis, whereas fat seemed to be uninvolved in the process. Eighteen different amino acids were found in the autolysing mycelium of A. flavus. The general picture was of decreasing concentrations during autolysis, and amino acids decreased their content by about 95% with respect to the concentration present at the beginning. This decrease partially accounted for the loss of mycelial-nitrogen observed during autolysis.

SUMMARY: Treatment of the naturally occurring magno-inducible Staphylococcus aureus strain 8325-18 with ethyl methane sulphonate allows the isolation of mutants which synthesize much less penicillinase than the parent. Both inducible and constitutive mutants can be isolated and their activities range from 0.1 to 50% of the basal activity of the wild type. All the mutants examined here synthesize a penicillinase indistinguishable from the wild type in terms of substrate profile and reaction with specific anti-exo-penicillinase serum. Examination of the genetic make-up of the mutants shows that they all possess an intact inducibility (i +) gene. It is theoretically possible that the lesion in the micro-inducible strains could lie in the penicillinase structural gene, but such a location is extremely unlikely for the micro-constitutives. The most likely location for these mutants is a region analogous to the operator of the lactose segment of Escherichia coli; however, their properties are incompatible with the recent suggestion that the operator region should be divided into two distinct parts.

SUMMARY: The growth of phage λ.C (i.e. phage λ grown in Escherichia coli c) in E. coli k lysogenized by phage P1 is normally restricted so that the efficiency of plating of phage λ.C on K (P 1) compared to C is about 10−7. When k (p 1) bacteria are heated before infection with phage λ. C this restriction may be decreased as much as a million-fold. The time of exposure to elevated temperature (49° and above) required to achieve this increase in e.o.p. of phage λ.C decreased with increasing temperature up to temperatures which began to inhibit the capacity of bacteria to grow phage. Heated k (p 1) bacteria recovered their ability to restrict phage λ.C following the resumption of growth at 37°. Part of this recovery can be inhibited by chloramphenicol. A more dramatic recovery of restriction is observed when heated k (p 1) bacteria are resuspended in hypertonic media. Experiments are described which indicate that phage λ.C is restricted at an early step after adsorption and that, if phage escapes this restriction, it can grow in heated bacteria subsequently converted into restricting hosts by resuspension in hypertonic media.

SUMMARY: Biosynthetic precursors of carotenoids and hydroxylated carotenoids were substituted for sterol in growth experiments with two representative sterol-requiring mycoplasmas, Mycoplasma hominis, strain 07 and avian Mycoplasma sp., strain j. Only C40 dihydroxyl compounds but not biosynthetic precursors supported growth of M. hominis. These results suggested that all enzymes in the biosynthetic pathway to carotenoids were lacking in this organism. A slight response to phytoene and neurosporene indicated that this species may be capable of hydroxylation of C40 compounds. Certain precursors of carotenoids and C40 dihydroxyl carotenoids supported growth of avian strain j. The phosphorylated mevalonic acids did not support growth of this organism, while isopentenyl pyrophosphate produced a response. These results indicated that an enzymic block occurs between mevalonic acid and isopentenyl pyrophosphate. Phytoene, phytofluene, ζ-carotene, and neurosporene supported growth of this organism indicating that enzymes probably are present for the conversion of certain C40 intermediates to dihydroxyl C40 compound(s). Lycopene and β-carotene did not support growth probably due to the lack of hydro-xylating enzymes for these carotenoids. Monohydroxyl C40 carotenoids produced a negligible growth response with both organisms. The growth response of both organisms to sarcinaxanthin and lutein indicated that the presence of two hydroxyl groups in the 3,3′-positions is essential for growth. That the carotenol of M. laidlawii strain b supported growth is further proof that a dihydroxyl C40 compound is required for growth (the exact locations of the hydroxyl groups are unknown). Since earlier work has suggested analogous functions for sterol and carotenol the sterol requirement of certain mycoplasma species appears to be the result of the inability of these organisms to effect biosynthesis of carotenols.

SUMMARY: The electron microscope shows that there are a number of different morphological types of bacteriophages which grow on Pseudomonas aeruginosa. Some are conventional ones with contractile or non-contractile tails, but the most interesting is a tail-less phage containing RNA. The structure of both conventional and RNA phages is described. It is shown that the RNA phage probably infects the cell via polar pili. Intracellular multiplication and lysis by the RNA phage is followed in thin sections of infected cells. In the early stages, the nuclear region is much reduced and dense granular areas appear. These subsequently differentiate into crystalline aggregates of virus particles; at the same time a large bulge, identical to that found associated with spheroplast formation, appears. The crystals continue to increase in size until the spheroplast ruptures and lysis occurs.

SUMMARY: Escherichia coli strain B was sensitized to the action of γ-radiation or ultraviolet (u.v.) radiation by incorporating 5-bromouracil into the DNA of the bacteria. Most sensitization was observed after u.v. irradiation, less after anoxic γ-irradiation and least after aerobic γ-irradiation. Incubation of the bacteria for a few hours after irradiation on a nutrient medium which included chloramphenicol generally resulted in extensive restoration of colony-forming ability whether or not the bacteria contained 5-bromouracil. Only after the aerobic γ-irradiation of bacteria containing no bromoruacil was little restoration obtained, After aerobic or anaerobic γ-irradiation the ‘rescue’ of bacteria containing 5-bromouracil was relatively larger than that observed for bacteria containing no bromouracil. Maximum restoration was obtained after u.v. irradiation and this occurred to about the same extent, whether or not bromouracil had been incorporated into the bacteria. The results suggest that treatment with chloramphenicol decreases the expression of radiation-induced lesions which occur in the bacterial DNA; this may account for the mechanism of action of the inhibitor.

SUMMARY: The major characteristics of a temperate phage specific, as far as is known, for one strain of Escherichia coli serotype 04 have been described. It is inactivated by ultraviolet light at a rate characteristic of temperate phages, and it is serologically unrelated to the P1, P22 and T phages. This phage (designated ø 04–CF) is short-tailed, contains DNA, is about 55 mμ, needs no supplemental Ca2+ or Mg2+ for adsorption, shows a latent period of 46 min. and a burst size of 166, and is ultraviolet light inducible. Phage 04-CF can transduce markers to the susceptible indicator strain of E. coli (CF 2004-6). The variety of markers transduced indicates that this is another generalized transducing system for E. coli. The frequencies of transduction lie between 10−6 and 10−8 for different markers, but vary with phage multiplicities. This strain of E. coli also acts as recipient in matings with E. coli K 12 strains.

SUMMARY: The major characteristics of a temperate phage specific, as far as is known, for one strain of Escherichia coli serotype 04 have been described. It is inactivated by ultraviolet light at a rate characteristic of temperate phages, and it is serologically unrelated to the P1, P22 and T phages. This phage (designated ø 04-CF) is short-tailed, contains DNA, is about 55 mμ, needs no supplemental Ca2+ or Mg2+ for adsorption, shows a latent period of 46 min. and a burst size of 166, and is ultraviolet light inducible. Phage 04-CF can transduce markers to the susceptible indicator strain of E. coli (CF 2004-6). The variety of markers transduced indicates that this is another generalized transducing system for E. coli. The frequencies of transduction lie between 10−6 and 10−8 for different markers, but vary with phage multiplicities. This strain of E. coli also acts as recipient in matings with E. coli K 12 strains.

SUMMARY: Some characteristics of protoplast extrusion from hyphae of Fusarium culmorum are described. One, two or more protoplasts might be released from one mycelial compartment. The release was stimulated by controlled dilution of the stabilizing solution. NH4Cl and mannitol were the best stabilizers of those tested. Connecting threads between protoplasts were observed; their meaning is discussed. Changes in the growth medium did not affect mycelium sensitivity for protoplast formation. Various stages of a protoplast fusion process were followed. Protoplast fusion usually began by an attraction of two bodies followed by junction and fusion to give a single large body. There was no evidence that these fusions represent a sexual process. Fusion of protoplasts in Fusarium is infrequent.

SUMMARY: The growth of Aerobacter aerogenes cultures in a chemostat under conditions of K+-limitation was investigated. At a fixed dilution rate there was a linear relationship between bacterial concentration and the K+ concentration in the culture. The extrapolated plot did not pass through the origin, however; this indicated the presence in the medium of substance(s) supporting some growth in the absence of K+. The growth yield varied markedly with the dilution rate; bacterial concentration decreased and the cellular K+, Mg2+, RNA and phosphorus contents increased as the ‘steady-state’ growth rate was increased. The yield variation was similar to that observed when either Mg2+ or PO4 3- was the limiting component of the medium. Analysis of K+-limited organisms revealed a molar stoichiometry between cellular Mg2+, K+ and P (close to 1:4:8, respectively) that was almost independent of growth rate. It is suggested that a precise intracellular K+:Mg2+ ratio may be of importance for maintaining ribosomal structures in a suitable functional configuration or degree of aggregation, and it is for this purpose that high concentrations of K+ are present in growing bacteria. K+-limited A. aerogenes cultures oxidized glycerol rapidly, as did washed supensions of these organisms in phosphate buffer (pH 6.5). Glycerol (10 mm) accelerated the death-rate of K+-limited bacteria; potassium (15 mm) and magnesium (15 mm) each decreased this glycerol toxicity and, when added together, abolished it. The death-rate of washed K+-limited A. aerogenes suspensions in phosphate saline (pH 6.5) was a function of their ‘steady-state’ growth rate.

SUMMARY: The ultrastructure of Lupinus luteus L. and Ornithopus sativus Brot. root nodules derived from infection by Rhizobium lupini strain D25 was examined. In both cases the associations produced completely effective nodules but their gross morphology was markedly different. Bacteria within the O. sativus nodules were enclosed in groups by a membranous envelope, and the bacteria had electron translucent regions. Bacteria within the L. luteus nodules were enclosed singly and did not exhibit similar electron translucent regions. Starch granules were observed within infected cells of L. luteus but not within uninfected cells; the reverse was observed in O. sativus cells.

SUMMARY: In contrast to other members of the influenza virus group, a strain of fowl plague virus produced large amounts of intracellular haemagglutinin in the chorioallantoic membranes of infected chick embryos. The titres of intracellular haemagglutinin obtained with the fowl plague virus were 400-2000-fold higher than those of the human influenza viruses tested. The fowl plague virus also differed from the human influenza viruses in being capable of growing through the chorioallantoic membrane when inoculated by the chorionic route. The only other myxovirus so far discovered that elicited a high intracellular haemagglutinin titre was Newcastle disease virus, although this type of virus is neither serologically nor morphologically related to the influenza viruses.

Electron microscopic investigations of membrane specimens from embryos infected with fowl plague virus showed the presence of a large number of structures, ranging in size from 300 Å to more than 7000 Å, with a surface configuration indistinguishable from that of the envelope component of typical particles. Similar structures were found very rarely in specimens of membranes infected with the human influenza viruses.