- Volume 33, Issue 2, 1963

SUMMARY: I feel much honoured to have been invited to give the Marjory Stephenson Memorial lecture of 1963, but I must confess that I also approach the undertaking with considerable trepidation as it fills me with an acute sense of inadequacy.

SUMMARY: A strain of Aspergillus amstelodami, which antagonized the growth of Mycobacterium tuberculosis, was shown to produce at least two antibiotic substances. A liquid medium was developed for their production, and cultural and assay procedures were defined. The antibiotics appear to be distinct from previously described derivatives of the true fungi and were named Amodin A and Amodin B. Both are active against certain Grampositive and acid-fast organisms, but Amodin B has the wider antibiotic spectrum and is active against some Gram-negative organisms and strains of Candida albicans. Amodin A was produced in surface and submerged cultures, but in better yield in the latter; it was extracted and prepared as a crude product. It appears to be a moderately heat-labile peptide; though non-toxic to mice it did not prolong their survival when infected with Staphylococcus aureus or M. tuberculosis at the dosage of antibiotic used. Amodin B appeared only in surface cultures and was mainly present in the mycelium, from which it was liberated by dilute acid. It is relatively heat-stable and not inactivated by proteolytic enzymes. Amodin A production appears to be linked with the conidial mode of sporulation and Amodin B with the perithecial mode.

SUMMARY: The frequency of transduced cells (gal +) was reduced by the transfer of the Salmonella typhimurium recipient cells with adsorbed P22 transducing phage from a complete into a minimal medium. This reduction was most conspicuous immediately after the adsorption of the phage (3 min.) and then gradually decreased as transfer was delayed. After cultivation for 90 min. under conditions which permitted growth and multiplication of the cells the frequency of the transduced cells was practically no more influenced. The sensitivity of the potentially transduced cells to acriflavine was assayed soon after the adsorption of the phage. An early acriflavine-reversible phase was demonstrated in more than 50 % of transductions. A close time relationship was found between shift-reversible and acriflavine-reversible phases.

SUMMARY: The experiments described establish the importance of the pentose cycle in carbohydrate breakdown by Staphylococcus aureus. No Entner-Doudoroff pathway was found. Another feature is the extensive glucose effect: growth in glucose enhanced glycolysis suppressed the Krebs cycle, decreased the activity of the pentose cycle and suppressed the formation of many enzymes. Even the oxidation of pyruvic acid was decreased in glucose-grown organisms. The decrease of oxidative activity affected the cytochromes. The main products of carbohydrate oxidation were acetic acid and carbon dioxide. The accumulation of acetic acid indicated that the link between pyruvic acid and the citric acid cycle was weak.

SUMMARY: In stock cultures of Salmonella typhimurium strain lt2 carrying the factor determining the production of colicine I, colI, together with other colicine factors, colE1 or colE2, most of the small minority of bacteria competent to act as donors of colI also transmit their E factor. Most noncolicinogenic bacteria which acquire an E factor at the same time as colI become competent to transmit both factors. Similarly, bacteria carrying factors colE1 and/or colE2 accept colI normally and then usually become competent to transmit both colI and the E factor(s) they already carry. In experiments on the kinetics of colicine factor transmission by lt2 (colE1) (colE2) newly infected with colI, most acceptor bacteria that acquire any colicine factor acquire all three factors, within 5–20 min. for most pairs, but within 1 min. for a very few. When conjugation is interrupted within 5 min. of mixing, fewer acceptor bacteria acquire all three factors; all single-factor and two-factor classes are then represented, so the order of transfer of the three factors must differ in different pairs. Bacteria carrying colE2 do not transfer this factor to donor bacteria from whom they acquire colI; but they become able to transmit colE2 (and presumably colI also) within 15–20 min. of acquiring colI. Other observations support the hypothesis that in most competent donors carrying colE1 and/or colE2, these factors multiply autonomously, as does colI.

SUMMARY: The base composition of purified DNA from 28 strains of acetic acid bacteria was determined. Most strains of the genus Gluconobacter clustered closely together at 60.6–63.4 % (guanine + cytosine) of total base. All strains of the Acetobacter aceti biotype lay within the range 55.4–64.0 % (guanine + cytosine). The close relationship and possible common phylo-genetic origin of the genera Gluconobacter and Acetobacter is again stressed by these results. The base composition of DNA from acetic acid bacteria and from species of Pseudomonas was very similar, confirming the suspected close relationship between these groups. There is a noticeable agreement between the sequences of Acetobacter strains, arranged according to increasing % (guanine + cytosine) and arranged according to increasing enzymic equipment: strains with greater biochemical activity have on the whole also a higher % (guanine + cytosine) in DNA. The range of the compositional distribution of DNA molecules is on the whole broader in Acetobacter than in Gluconobacter. The results corroborate previous conclusions that both biotypes contain clusters of strains without species differentiation. A comparison of the paper chromatographic analysis with the method of thermal denaturation (‘melting point’) for estimating base composition of DNA showed that the latter method was to be preferred in routine analysis because of its ease, rapidity and reproducibility.

SUMMARY: A particulate enzyme fraction from type VIII Pneumococcus obtained by centrifugation of disrupted organisms between 30,000 and 140,000 g synthesized a non-reducing disaccharide from uridine diphosphoglucose (UDPG). The structure proposed for the material synthesized is gluco-pyranosyl-glucopyranoside, in which at least one of the linkages is of the β configuration. The reaction may be formulated as: UDPG + UDPG → glucopyranosyl-glucopyranoside. The reaction was not type-specific and was also found with particulate fractions from pneumococci of types II and III.

SUMMARY: Forty-two strains of ‘Bacterium salmonicida’, six of a non-pigmented fish pathogen and forty-two Aeromonas strains were compared morphologically, culturally, biochemically and metabolically. The results, which were computed electronically, showed a distinct difference between ‘B. salmonicida’ and the Aeromonas species. On the grounds of this variation in morphology, culture and biochemistry, it is suggested that ‘B. salmonicida’ be removed from the genus Aeromonas and given a generic place in the family Pseudomonadaceae. The name Necromonas salmonicida is suggested as an alternative to ‘B. salmonicida’.

SUMMARY: The agar gel diffusion technique was used to investigate the serological relationships between species and strains of Streptomyces. A method is described for the rapid production of antisera which show specific reactions and also a multiplicity of cross-reactions. The technique has been used for the identification and comparison of antibiotic-producing isolates of streptomycetes from soil.

SUMMARY: A radiosensitive mutant of Escherichia coli strain K12, W3747 was found to be similar to E. coli strains b and s with respect to survival following ultraviolet irradiation, plating-medium recovery, ability to ‘reactivate’ irradiated T1 phage, and in its cross-resistance pattern with radiomimetic chemicals. In all these respects the radiosensitive E. coli strain k12, ab1186, isolated by Howard-Flanders, was found to resemble the Hill radiation hypersensitive strain Bs-1, and, except in the ability to reactivate irradiated T1 phage, strain B s-2. Strains W3747s and ab1886 acquired sensitivity to radiomimetic chemicals concomitantly with radiation sensitivity. Strains Bs-1 and Bs-2 on becoming hypersensitive to radiation did not become correspondingly hypersensitive to radiomimetic chemicals. In fact, they acquired a small degree of resistance to these chemicals, relative to strain B, and a substantial increase in resistance to 1-methyl-3-nitro-1-nitrosoguanidine and proflavine. These results are discussed in terms of known genetic loci implicated in radiation sensitivity and resistance.

SUMMARY: A group of intersterile strains (R-) have been identified in Streptomyces coelicolor Strain a3 (2). They give fertile crosses with other strains (R+) which in turn are fertile among themselves. In R- x R+ crosses the contribution of R+ markers to the recombinant progeny is usually small. The fertility factor(s), which cannot be eliminated by acridine dyes, may be transferred at high frequency in R+ x R- crosses, but the fertilized strains display a low fertility.

SUMMARY: During the formation of incomplete fowl plague virus, normal amounts of viral compounds are synthesized. The S-antigen, however, cannot be demonstrated within the cytoplasm in appreciable amounts by fluorescent antibody. The oligonucleotide pattern and the specific radioactivity of the ribonucleic acid (RNA) of incomplete forms are almost identical with those of standard virus. In contrast to chemically inactivated viruses no indication of multiplicity reactivation was found with incomplete forms. It is suggested that the incomplete forms are lacking in identical pieces of their genome, but contain that part of their RNA which codes for ‘early protein’, S-antigen and haemagglutinin.

SUMMARY: The sodium azide resistance of Proteus hauseri is not of the all-or-none unilocal type reported for Escherichia coli but rather of the obligatory multi-step or penicillin variety. Independently isolated 1st-step resistant variants possessed similar degrees of resistance to sodium azide. Some properties of azide-resistant variants of P. hauseri are described. In support of the above finding it was possible to transduce 1st-step (and only 1st-step) resistance into the wild-tpye by phage grown on either 1st-, 2nd-, 3rd- or 4th-step resistant organisms. It was also possible to transduce 2nd-step resistance into 1st-step organisms by phage developed on independently isolated 1st step resistant organisms or by phage from multi-step resistant. About 60 % of transduced genes expressed their phenotype in platings done immediately after the adsorption period. It is concluded that a number of loci, not closely linked, and possibly equipotent, control sodium azide resistance in P. hauseri and that resistance could be dominant to the wild allele.

SUMMARY: All but four of twenty-five strains of Staphylococcus aureus exposed to concentrations of 60 μg. benzylpenicillin/ml. (or 100–500 μg. methicillin/ml. for penicillinase-producing strains) on nutrient agar media containing 3.5 % (w/v) sodium chloride and 10 % (v/v) horse serum, gave rise to typical L colonies. The L forms were subcultured on nutrient agar and in broth containing 3.5 % sodium chloride and were found to be completely resistant to the penicillins, cycloserine, ristocetin, vancomycin and cephalosporin, but to be sensitive to other antibiotics, often in slightly lower concentrations than the parent cocci. The L forms produced coagulase and, in two of three strains tested, were lysogenic although resistant to phage lysis. In studies of the transformation of staphylococci to L forms, it was noted that a variable but often very large proportion of the early L microcolonies failed to develop into typical colonies.

SUMMARY: Large transient increases in the concentration of some dry airborne spores coincident with the start of rain suggested that the first raindrops to wet surfaces might disperse spores other than in splash droplets or by wetting fructifications. Experimental collisions between glass beads or water drops and spore-bearing surfaces showed that both rapid air movement in advance of radially spreading splashes and vibration can suspend spores in air. Removal by air movement is most effective when large drops collide with surfaces carrying spores that are loose or raised above the surface.

SUMMARY: Sphaleromantis tetragona Skuja, which has not been previously reported for Britain, is described with the use of the optical and the electron microscopes. The organism possesses an elaborate sheath which is not visible with the optical microscope; the sheath is probably made of organic material. Cell division and cyst formation are described. The cyst, not previously known, is described as seen with the optical microscope.