- Volume 17, Issue 1, 1957

Summary: The occurrence has been studied of mutants which did not produce extracellular cellulose in cultures of two strains of Acetobacter acetigenum (NCIB8132, NCIB5346) and one strain of A. xylinum var. africanum (NCIB7029). With about 150 glucose yeast-extract (GYE) medium static cultures of organism NCIB8132, prepared over a period of about one year, cellulose pellicles were produced in each case. In contrast, the loss of cellulose-forming ability and the appearance of diffuse general growth were noted with 6 out of 26 tests made with static cultures in an ethanol yeast-extract (EYE) medium, 3 out of 905 isolates selected from platings of GYE shaken cultures, and 1 out of 3 tests made with EYE shaken cultures. By a ‘mass-plating’ technique it was found that mutants which did not produce cellulose pellicles (‘celluloseless mutants’) were present in cellulose-producing cultures. The two other cultures (NCIB5346, NCIB7029) underwent mutation spontaneously in GYE static cultures on several occasions.

Summary: The classical strain of herpes simplex virus (Burnet & Lush, 1939) and a recently isolated strain (Melbourne 1/56) were propagated in tissue culture of human amnion and infant-mouse kidney ‘epithelial’ cells. Following the inoculation of 103·25 TCCD50 (tissue culture cytopathogenic dose) of the Melbourne 1/56 herpes simplex virus into amnion cell culture, the titre of virus dropped to 100·50 TCCD50 at 12 hr. and the maximum level of virus (103·50 TCCD50) was detected at 48 hr. after inoculation. The earliest morphological changes were observed in the tube-cultures c. 18 hr. after inoculation of the virus and eosinophilic intranuclear inclusion bodies were observed in the amnion cells c. 24 hr. after virus injection. Cell degeneration was prominent at 36 hr. when most cells were highly retractile and rounded. Cell suspensions, harvested from infected and uninfected cultures of amnion and mouse- kidney epithelium, were treated with immune herpes serum followed by fluorescent rabbit anti-human γ-globulin, and specific peripheral fluorescence was observed in the unfixed preparations of the infected tissue cultures. The limited surface staining was ascribed to the impermeability of the unfixed cytoplasmic membranes to globulins.

Summary: During passage of the influenza A strain CAM in eggs in the presence of anti-CAM serum, three true-breeding variants were isolated. The variants Ic, Is and SP7 showed increasing resistance to inhibition by anti-CAM serum. The evidence indicated that virus population changed in the course of passage as a result of the appearance of successive variants capable of preferential survival in the experimental environment. The strains Is and SP7, unlike the parent strain CAM, were pathogenic for mice inoculated intranasally. The implications of these findings are discussed.

SUMMARY: An account is given of the development of a reliable method for the isolation of Streptococcus pluton (Bacillus pluton White), an organism associated with European foul-brood disease of the larval honeybee. S. pluton, isolated as an anaerobe, may be trained to grow as an aerobe in rod form. Its principal anaerobic growth requirements are a low molar ratio of Na: K, high inorganic phosphate concentration, glucose or fructose, and undetermined factors provided by yeast extract. Peptones are harmful to growth. Aerobic growth has no very critical requirements other than glucose, fructose or sucrose. Bacterium eurydice White which, together with S. pluton, causes European foul-brood disease grows well anaerobically on a yeast extract + glucose + fructose medium; either sugar alone supports only feeble anaerobic growth. Anaerobic growth of B.eurydice is also accelerated by a low molar ratio of Na: K and is inhibited by peptones. S. pluton and B.eurydice appear to be separate organisms; no evidence has been obtained to support claims by previous workers that S. pluton is a variant of B. eurydice.

Summary: Studies by cinemicrography confirm that the long forms of Proteus vulgaris (Hauser) seen during the swarming stage are morphologically indistinguishable from those induced by penicillin and other toxic agents. They appear only in cultures which are growing freely and when a threshold concentration of population has been reached; thereafter the organisms at the growing edge of the colony become more abnormal with each swarming. The normal small bacilli may begin to move before any long forms are present. In later swarmings, movement may be seen in small as well as in long organisms. It is suggested that the long forms are induced by a non-specific volatile agent which can not be detected when growth has been cleared from the medium. Its action is enhanced in cultures which are confined under a coverslip. Though it is partially neutralized by the action of catalase, conclusive proof of its nature is still lacking. When different strains are grown together long forms are soon produced. The agents causing this are specific and stable, producing their effect immediately, and are detectable in the medium after the primary culture has been cleared from it.

Summary: Of 13 sulphur-containing compounds tested only cystine, cysteine and glutathione satisfied the sulphur requirements of the strains of Haemophilus pertussis used when grown in a defined liquid medium containing 15 amino acids. Very small inocula (3–10 viable organisms) of 8 strains grew in a medium containing glutamic acid + cystine as the only amino acids added. Four strains were carried through 9 subcultures in this medium.

Summary: When cultivated on membranes for electron microscopy, in the presence of 800 units penicillin/ml. and 10% (v/v) horse serum, a strain of Proteus vulgaris developed L-colonies in two stages. In the first cultures, the colonies consisted of naked protoplasts with a wide periphery of relatively disorganized protoplasm, and when further subcultured upon penicillin the entire colonies consisted of disorganized protoplasm. The typical bacillary form could be recovered by subculture of this material upon penicillin-free medium. In the process of regeneration the cultures passed initially through a stage in which they again consisted of protoplasts.

SUMMARY: Preparations of Paramecium aurelia, which had been immobilized by placing the organisms in a solution containing antiserum conjugated with fluorescein (conjugated antiserum), were examined by fluorescence microscopy. Unfixed paramecia accumulated fluorescent antibody in a thin layer around the entire surface of the organisms, and in globules at the clumped tips of the cilia, but not in the cilia themselves. No fluorescence was seen in the nuclei or the cytoplasm, but the food vacuoles became brightly fluorescent when the paramecia remained in conjugated antiserum for a few hours. Paramecia, which had been fixed with osmic acid and subsequently treated with fluorescent antibody, showed a faint fluorescence along the whole lengths of the cilia. When transformation from one serotype to another took place, the change in ability to take up a given kind of fluorescent antibody was seen to occur uniformly over the whole surface of the organism. It is concluded that the immobilization antigen is a fluid substance which covers the whole surface of the paramecia and is exuded into the medium under certain conditions, especially when homologous antibody is present.

SUMMARY: A method for the preparation of carbon replicas of Bacillus spores is described. Micrographs of these replicas reveal much more of the surface detail than direct electron micrographs. Rib formations were found on five different species and the micrographs obtained suggest that the sculpturing varies according to the species.

SUMMARY: Studies of the products obtained when tobacco mosaic virus (TMV) is disrupted with alkali or phenol suggest that immunological specificity is primarily an attribute of the protein and infectivity of the nucleic acid. Although exposing the virus to alkali produces infective fragments, it also causes much inactivation, and much of the nucleoprotein sedimented when preparations are ultracentrifuged at pH 6 is not infective. The unsedimented protein fragments are inhibitors of infection; from such unsedimentable material, which at 5 g./l. produced no lesions when inoculated to Nicotiana glutinosa, some infective nucleoprotein could sometimes be separated by precipitation with ammonium sulphate, followed by ultracentrifugation. The infectivity of fragmented TMV is ephemeral, but it is stabilized when the fragments are reunited. Nucleic acid preparations made by phenol are quickly inactivated by ribonucleases from pancreas or leaves; pancreatic ribonuclease also inactivates alkali-made fragments, but the infectivity of these is stabilized by leaf ribonuclease. Phenol-made preparations are much less infective per unit of phosphorus than intact TMV, but measurements of the relative infectivities of the two kinds of inocula are complicated because the two respond differently to dilution and they are not equally able to infect N. glutinosa leaves in different physiological states. Although urea does not inactivate phenol-made preparations, nucleic acid made by exposing TMV to urea has little or no infectivity. The possibility that infective TMV can be reassembled in vitro from previously non-infective components cannot be excluded, but all the results that could be interpreted as suggesting this are also interpretable in other ways, either by the removal of inhibitors of infection or by the stabilization of infective fragments that otherwise would have become inactive before testing.

SUMMARY: Sixty Streptomyces isolates which produce polyene antibiotics were isolated from 25 soil samples collected in different parts of the world. Of these isolates 25 produced tetraenes, 23 produced pentaenes, 1 produced a hexaene, and 15 produced heptaenes. One isolate produced simultaneously a tetraene and a pentaene, another produced a tetraene and a heptaene, and a third produced a tetraene, a pentaene and a heptaene. The antibiotics showed activity against a wide range of fungi; the minimum inhibitory concentrations against Saccharomyces ceremsiae, Aspergillus niger, Mucor racemosus, Candida albicans, Fusarium culmorum and Trichophyton mentagrophytes are given for 10 of them. The distribution of activity between culture filtrate and mycelium is given for 14 of the antibiotics.

SUMMARY: A single mesophilic species of a new genus belonging to the family Streptomycetaceae of the order Actinomycetales is described and has been named Waksmania (W. rosea, type species). It produces a filamentous growth which is differentiated into vegetative (primary) mycelium and aerial (secondary) mycelium. Hyphae are 1·5 μ. or less in diameter. The new genus is characterized by the production of pairs of spores which are formed either: (1) at the tip of sporophores which branch from an aerially borne hypha; or (2) directly on an aerial hypha. Spores are not formed on the vegetative mycelium.

SUMMARY: The staphylococcal typing-phage 42 D is propagated on bacteria which are lysogenic for the phage 1363, and the latter phage is present as a contaminant in preparations of phage 42 D. This contamination can be avoided by propagating a pure clone of phage 42 D on non-lysogenic organisms. Such nonlysogenic propagating strains can be isolated after the lysogenic propagating organisms have been irradiated heavily with ultraviolet radiation.

SUMMARY: A method of cultivating fungi on a membrane filter is described. The growth on the membrane appears to be more rapid than on solid media. After 2–3 days of growth a piece of the disk was dried and placed in immersion oil on a slide, thus rendering the membrane transparent and suitable for microscopic examination in transmitted light. The new method makes the use of plates, microcultures (slide cultures), etc., unnecessary. The mechanical breakage of the mycelial structures often encountered when species of mycelium have to be transferred to slides for microscopic examination is avoided. As only a small piece of the membrane is needed for microscopic examination, the growth on the membrane is allowed to continue as long as is required. Each time an inspection of the culture is required, a small piece of the disk is removed.

SUMMARY: Extracts of the polyphenolic fractions of the water-soluble metabolites (that is, the complex mixtures of plant phenols extracted by ethyl acetate) were prepared from apple and pear varieties characterized by different degrees of resistance to the scab pathogens. Qualitative differences were chiefly interspecific and extracts of resistant varieties did not contain major components lacking in those of less- resistant varieties of the same species. Cultural reactions of distinct clones of each pathogen to the extracts, in the presence of various basal media, were observed. Growth and sporulation were inhibited independently by extracts of less-resistant as well as resistant host varieties. The clones were not equally susceptible, those of Venturia inaequalis showing relationships between inhibition of sporulation by host polyphenols and their varietal host ranges. Fluctuations in pathogenicity of a clone of V. pirina during storage in culture with periodic re-isolation from Williams pear were reflected in its reactions to the extracts. Both pathogens were capable of decomposing the polyphenols. The results suggested that qualitative and quantitative variations in the polyphenolic host metabolites, including differences in their relative proportions, in relation to nitrogenous and other nutritional factors, are of potential significance in the determination of pathogenicity and varietal resistance.

SUMMARY: The air over an arable field at Rothamsted Experimental Station, Harpenden, was sampled from 1 June to 25 October 1952 at 2 m. above ground with an automatic volumetric spore trap. Each day’s slide was scanned and all the spores counted on an area representing a sample volume of 41l. of air. Spores were classified in 20 morphological groups and a miscellaneous one. Seasonal periodicities are presented as 6-day running means of the daily average number of spores/m.3 air, and then related to meteorological data. Cladosporium conidia accounted for 46 % of the total catch; hyaline basidiospores (chiefly Sporobolomyces) for 31 %; and pollen only 1 %. The relative frequency of various spore types differs from that recorded by earlier workers because the suction trap catches spores of all sizes with almost equal efficiency and is little influenced by external conditions. The results which should be representative of large rural areas of central and south England show that the major changes of spore concentration depend on the weather and the phenology of the local vegetation and its associated fungal flora. During 24 days in late June and July comparable estimates of spore concentration were made with another trap 24 m. above ground. The spore concentration of the twelve commonest groups at 24 m. totalled 82 % of that at 2 m.

SUMMARY: The optimal conditions for accurate and reproducible analysis of cellulose hydrolysis by micro-organisms, particularly from the rumen, were determined. Rumen micro-organisms were found to require approximately 50 mg. substrate (cellulose powder) in a 40 hr. incubation at 37° with 1 ml. of rumen liquor, and a total volume of 8 ml., in static vessels. All types of cellulose Or simpler substituted derivatives, from soluble carboxymethylcellulose through insoluble cellulose powder to cotton fibres, are nearly quantitatively hydrolysed by mixed rumen micro-organisms. The effect of the inorganic composition of the medium, of antibacterial agents (thymol, fluoride, toluene) and of concentration procedures on the cellulolytic activity of rumen micro-organisms was examined. Rumen protozoa appear to play a minor role in cellulose degradation; their effective activity is due mainly to closely associated, possibly ingested, bacteria. The validity of the results obtained by various methods of ‘cellulase ’ assay is discussed.

SUMMARY: A study has been made of the degradation of different forms of cellulose (‘eellulolysis’), comprising soluble substituted derivatives (carboxymethyl-cellulose), insoluble cellulose powder, swollen cellulose, hydrocellulose and native cotton fibres, by concentrated suspensions of mixed rumen micro-organisms and by the aerobic fungus Myrothecium verrucaria. Mixed rumen micro-organisms are shown to be one of the most powerful sources of cellulolytic enzyme, in that they produce almost complete solubilization of all the above forms of cellulose in a relatively short period (3 days). Enrichment cultures of rumen micro-organisms were prepared by growing concentrates of mixed micro-organisms on cellulose powder. Cellulolysis was followed by determining the cellulose disappearance, formation of cellulolytic activity and gas evolution. Freeze-dried powders and their derived acetone powders obtained from washed concentrated supensions (non-enrichment cultures) of mixed rumen micro-organisms solubilized up to 80% of insoluble cellulose powder. Cell-free extracts were isolated: (a) from concentrated suspensions and from freeze-dried powders of rumen micro-organisms by extraction with butanol; (b) from concentrated suspensions of enrichment cultures by grinding with alumina at low temperature. The butanol extracts solubilized cellulose powder to a small extent (10% solubilization) and were more effective against the soluble carboxymethyl-cellulose. In contrast, the alumina extracts were more active against insoluble cellulose (30% solubilization) but were only weakly active against carboxymethyl-cellulose. Cell-free filtrates from Myrothecium verrucaria, an aerobic fungus much used in work on cellulose metabolism, were shown to possess cellulolytic properties very similar to those of alumina extracts from enrichment cultures of rumen micro-organisms. The significance of the results is discussed in relation to the mode of breakdown of cellulose.

SUMMARY: Scientific classification is virtually a branch of mathematics which describes the overall similarities of organisms. Catalogues do not do this. Many schemes of bacterial taxonomy are not classifications but catalogues. Similarity is best measured by the number of features in common between two strains, while division into taxa is based on correlated features. Other criteria for these two basic ideas are unsatisfactory and cause confusion, and there seems to be no logical reason why any one feature should be given greater weight in classification than any other. Hierarchical systems are a practical necessity, and simple mathematical methods are useful in bacterial classification. It is not necessary to know the evolutionary history of organisms in order to classify them in a scientific manner.