Showing papers in "Microbiology in 1972"

R factors from Proteus rettgeri.

Abstract: SUMMARY: Of 12 R factors transferred from wild strains of Proteus rettgeri to Escherichia coli K12, all were fi - Five were of the N-compatibility group; three belonged to a newly defined group T, of which Rts1 is the prototype; one belonged to group W. The other three constituted at least one compatibility group, not previously described. The replication of two of the T plasmids, like that of Rts1, was temperature sensitive. This set of R factors is significantly different from those derived from bacteria of other genera.

Non-smooth mutants of Salmonella typhimurium: differentiation by phage sensitivity and genetic mapping.

Abstract: SUMMARY: Non-smooth mutants of Salmonella typhimurium strain LT2 with known lipo-polysaccharide (LPS) defects were tested for sensitivity to smooth-specific phages (P22 and P22h and a newly isolated phage, 9NA, active on P22 lysogens); Felix O phage; and several rough-specific phages including C21. Smooth strains were sensitive only to the smooth-specific and Felix O phages. Six rfb mutants (unable to make O chains) were sensitive to Felix O and all the rough-specific phages except C21 (pattern R-sens). Of nine rfa mutants (presumed to have LPS core defects) four were R-sens, six were resistant to Felix O and some rough-specific phages (pattern R-res-1), and one was also resistant to phage Br2 (pattern R-res-2). The phage sensitivity of phosphomannoisomerase (pmi) mutants was the same as that of rfb mutants, except that they were partly sensitive to P22h. UDPgalactose-epimerase-negative mutants were sensitive to C21 and various rough-specific phages in-cluding Br2 (pattern Epi-i). An rfc mutant (unable to polymerize O repeat units) was sensitive only to Felix O and P221 (pattern Zsr). A part-rough mutant of class D (with abnormally few O chains) was incompletely resistant to smooth-specific phages, resistant to Felix O but sensitive to all rough-specific phages except C21 (pattern D-i). Spontaneous and mutagen-induced non-smooth mutants were isolated from lt2 strains with appropriate markers by selection with Felix O and/or P22 phage. (One parent strain used was non-lysogenic for Fels 2, for which lt2 wild-type is lysogenic. Lysogeny for Fels 2 did not affect sensitivity to the other phages.) Some mutants gave new sensitivity patterns. Mutants of these and of previously unmapped classes were crossed with smooth Hfr strains. The rfc loci of two mutants and pmi loci of two others were located in the gal-trp segment. Three mutants of pattern R-sens yielded O-specific hapten but mapped near his; they are believed to be unable to transfer O chains from antigen carrier lipid to the LPS core as a result of mutation at rfbT. Six mutants of pattern R-sens were smooth in cultural and serological properties; they mapped near his and are probably leaky rfb mutants. Many mutants had the class D part-rough phenotype, divisible by phage sensitivities into patterns D-1, D-2 and D-3. Mutants of all three classes mapped near xyl; they are likely to be rfa mutants, perhaps leaky, with LPS core defects which hinder but do not prevent attachment of O chains. Two classes were sensitive to C21 (WilkinsonS and rfaG mutants, resistant to Br2 (pattern Epi-2), unable to add the proximal glucose unit. Both loci mapped in or near the strA-xyl-metA segment. Several non-smooth mutants did not grow in the presence of bile-salts. Three mutants (rfaF) made LPS deficient of the distal heptose unit; one mutant (rfaE) was unable to add the proximal heptose unit. Both these loci mapped in or near the strA-metA segment.

The influence on numerical taxonomic similarities of errors in microbiological tests.

Abstract: SUMMARY: A study is made of the effect of experimental errors of microbiological tests upon similarity values used in numerical taxonomy. For the coefficient S SM approximations are given for the mean and standard error of similarity values when some test results are erroneous, S’, if the true value of similarity (S), the average probability in 1, 0 data of erroneous tests results (p), and the number of tests (n) are known. Formulae are given for estimating p from an analysis of variance, and for including or excluding chosen factors that affect test reproducibility. When p is over about 10% the error of similarity values becomes unacceptably large. Test error also increases the existing sampling error. It is generally better to employ many tests even if they are not as reproducible as desired, rather than to use only a few extremely reproducible tests. Examples are given suggesting that within one laboratory p can usually be kept below 5%, but the discrepancies between laboratories may often be much larger. It is advisable to replicate some of the strains in numerical taxonomic studies, so as to afford a check on test reproducibility.

Host Ranges of R Factors

Abstract: SUMMARY: All R factors so far described can be transmitted to Escherichia coli. F-like R factors are transmissible to the Proteus group but not to the Pseudomonadaceae. Among fi - R factors, I-like plasmids are not transferable to Proteus although they mediate conjugation, allowing transfer of other plasmids to this group. They are not transmissible to the Pseudomonadaceae. P-group plasmids are transmissible to both taxa. Plasmids of groups N and W are transmissible to Proteus (transfer to Pseudomonas was not tested because of lack of suitable markers).

Trimethoprim resistance conferred by W plasmids in Enterobacteriaceae.

Abstract: SUMMARY: High-level resistance to trimethoprim (minimum inhibitory concentration > 1000 μ/ml) was conferred by R factors of the W compatibility group in Escherichia coli and Klebsiella spp. isolated from patients in three London hospitals. We suggest that we are observing the early stages in the spread of a new R factor.

Nitrogenase Activity and Oxygen Sensitivity of the Paspalum notatum-Azotobacter paspali Association

Abstract: SUMMARY: Nitrogenase activity in the rhizosphere of a grass, Paspalum notatum, and its associated soil was measured by the reduction of acetylene. Roots of the cultivar ‘batatais’ colonized by Azotobacter paspali, when taken from the soil, produced 1 to 32 nmol C2H4/g dry wt/h, whereas the cultivar ‘pensacola’, which is not colonized by A. paspali, produced less than 0.5 nmol/g/h. There was a lag of 12 to 24 h before maximum, linear, rates of acetylene reduction were reached. Activity was almost completely inhibited in air or in the absence of O2 and was greatest at around pO2 0.04 atm. Activity of soil cores containing plants with leaves attached was little affected by pO2 and showed no lag. Soil-plant cores maintained in a 16 h day+8 h night showed no diurnal fluctuation in activity; as the dark period was extended, activity decreased but was restored on returning plants to the light. Roots and rhizomes had most activity, the soil very little and aerial parts none. Washing the roots removed less than half the activity. Disturbance of soil-plant cores decreased activity. The soil next to the root surface contained most A. paspali; more were associated with active plants than with less active plants. Sections of roots showed abundant bacteria adjacent to the root surface. Nitrogen fixation by the association was estimated to be up to 90 kg N/ha/annum.

Vegetative Incompatibility and Cytoplasmic Infection in Fungi

Abstract: SUMMARY: The effect of vegetative (heterokaryon) incompatibility on the transfer of a suppressive cytoplasmically determined condition, vegetative death, from carrier to normal strains of Aspergillus amstelodami has been investigated. Cytoplasmic transfer was reduced to 15% by vegetative incompatibility compared with 100% transfer in compatible combinations. Successful transfer in incompatible combinations involved donors and recipients whose incompatibility was determined by a single gene, and transfer was completely prevented between strains differing for more than one incompatibility gene. These results support the hypothesis that vegetative incompatibility serves as a cellular defence mechanism against genetic infection by stopping the spread of viruses and other suppressive cytoplasmic determinants from strain to strain in nature. Vegetative incompatibility is likely to be important in determining the specificity of virus-host interactions in fungi.

Inhibition of the Interaction Between Fimbrial Haemagglutinins and Erythrocytes by D-Mannose and Other Carbohydrates

Abstract: SUMMARY: Many monosaccharides, oligosaccharides and their derivatives were tested as inhibitors of agglutination of guinea-pig or horse erythrocytes by Salmonella typhimurium or Shigella flexneri bacteria bearing type-1 fimbriae. D-Mannose and certain derivatives of mannose were strongly inhibitory, and D-fructose moderately inhibitory. Modification of any of the hydroxyl groups at the C-2, C-3, C-4 or C-6 positions in the D-mannopyranosyl molecule caused failure to inhibit, showing that these groups were necessary for binding to the active sites of the fimbrial haemagglutinin. The α-configuration at the C-1 position in D-mannose was important and carbohydrates containing α-linked D-mannose were much more active inhibitors than those containing β-linked D-mannose, which were poor inhibitors or non-inhibitors. Yeast mannan also inhibited the fimbrial reaction. Attention is drawn to the remarkable degree of similarity of the inhibition pattern of the type-1 fimbrial haemagglutinin of bacteria with that of concanavalin-A, the jack bean haemagglutinin.

A morphological and genetic mapping study of white colony mutants of Streptomyces coelicolor.

Abstract: SUMMARY: Fifty whi mutants of Streptomyces coelicolor, having white instead of the wild-type grey colonies, were examined microscopically and genetically. The aerial mycelium structure of the mutants was broadly classified into six types, ranging from the complete absence of any stage of sporulation to the presence of apparently normal spores. Eight map locations were discovered for whi genes, all in previously well-marked regions of the map. Closely linked mutations possessed similar aerial mycelium structure, with few exceptions.

Absence of Laccase from Yellow-spored Mutants of Aspergillus nidulans

Abstract: SUMMARY: Green-spored strains of Aspergillus nidulans contain a p-diphenol oxidase (laccase) which is only formed during sporulation and is absent from yellow-spored mutants. The enzyme was assayed colorimetrically using N,N-dimethyl-p-phenylenediamine as substrate. Other substrates oxidized were pyrogallol, gallic acid and 2,6-dimethoxyphenol. Quinol, catechol and p-cresol were not detectably oxidized. Experiments with a temperature-sensitive yellow-spored mutant showed that the yA locus of A. nidulans is a structural gene for at least a component of the enzyme, while indirect evidence suggests that the enzyme also contains copper. Yellow-green-spored mutants of the ygA locus produce an inactive enzyme whose activity can be restored by dialysis against copper salts. Under certain conditions the enzyme itself can diffuse from a wild-type colony to a yellow-spored mutant colony and there act to give green spore pigment. From this it is deduced that the normal site of action of the enzyme may be external to the cell membrane. A similar enzyme has also been found in conidiating cultures of Aspergillus niger and Penicillium brevicompactum.

Chemotaxonomic Characters and Classification of Some Nocardioform Bacteria

Abstract: SUMMARY: Simple chemical analyses were carried out on 198 nocardioform bacteria by means of paper- and thin-layer chromatography. The strains considered to belong to the genus Nocardia contained the lipid LCN-A, arabinose and meso-diaminopimelic acid. All the representative strains from the ‘Mycobacterium’ rhodochrous complex possessed this lipid though in certain cases the characteristic spot had a slightly lower R F value than that of the reference lipid LCN-A from the standard strain of Nocardia asteroides. The genera Actinomadura, Mycobacterium, Oerskovia and Streptomyces did not contain lipid LCN-A and the distribution of the other two chemical characters varied. The method used to detect lipid LCN-A is simple and reliable and permits the separation of nocardias and ‘M.’ rhodochrous strains from allied taxa. These results correlate well with other trends in the taxonomy of nocardioform bacteria and confirm the value of chemotaxonomic characters, especially lipids, in the classification and identification of these organisms.

Sporulation in Bacillus subtilis. Characterization of oligosporogenous mutants and comparison of their phenotypes with those of asporogenous mutants.

Abstract: SUMMARY: An investigation was undertaken to determine to what extent the properties of oligosporogenous (Osp) mutants allow them to be considered as a separate class of sporulation mutant, distinct from asporogenous (Sp-) mutants. Of thirty Osp mutants examined, seventeen at least had a phenotype which had previously been identified with a Sp- mutant. The majority of cells in an Osp culture either reached a particular stage in the sporulation process and then stopped, or in some cases went on to produce aberrant forms. Some of these aberrant forms have their counterparts in Sp- mutants described by other authors, but some present new features. The morphological and biochemical sequences were linked so that if the majority of cells were blocked at a certain stage, then the biochemical sequence stopped accordingly. The general similarity in behaviour between the two types of mutant is consistent with the assumption that at least some of the Osp mutants have leaky mutations in genes where mutation can also give rise to Sp- phenotypes. Evidence is presented to suggest that the ability of a cell of an Osp mutant to overcome its block, and so go on to form a spore, is a chance event when that stage in the process is reached. A mutant has been obtained in which the spores are octanol-resistant yet contain no measurable dipicolinate. In several other mutants the spores contained well-developed coat layers, but the cortex was poorly formed or completely missing.

A co-operative numerical analysis of rapidly growing mycobacteria.

Abstract: SUMMARY: A co-operative numerical taxonomic analysis of rapidly growing mycobacteria of Runyon's group IV is reported. There was no limitation on the number, nature, or method of performance of the test characters contributed by each of the 12 participants. Initially 415 test characters were coded for analysis; deletion of irrelevant and repetitious data resulted in a final 195 characters used to generate the matching matrix. All nine major clusters defined in the study were of named species; however, three of these were noted to contain two or more species and the reduction of some of these to synonymy with prior epithets is discussed. Recognized clusters were: Mycobacterium smegmatis, M. phlei, M. vaccae (including M. para-fortuitum), M. diernhoferi, M. flavescens, the rhodochrous taxon, M. thamnopheos, M. fortuitum, M. chelonei. Results of the pooled information are compared with those of the individual participants. Immunological results generally correlated well with numerical analyses.

Polyene resistance and the isolation of sterol mutants in Saccharomyces cerevisiae.

Abstract: SUMMARY: Mutants of Saccharomyces cerevisiae have been selected for resistance to the polyene antibiotics, etruscomycin, filipin, nystatin, pimaricin and rimocidin. All mutants are resistant to nystatin and there are several patterns of cross-resistance. The mutants were allocated to four unlinked genes pol 1, 2, 3 and 5. A fifth gene, pol 4, was recovered as a double mutant with a strain carrying the pol 1 mutation. The pol 4 mutation does not cause resistance, pol 1 and pol 3 are allelic to the previously described nys 1 and nys 3 (Ahmed & Woods, 1967). There are correlations between the polyene used for mutant isolation and (i) the extent of cross-resistance; (ii) the selection of mutants at particular pol genes. Ultraviolet absorption spectra of non-saponifiable material extracted from representative mutants showed that all five genes affect the sterol composition of the cell. The major sterols found in pol + are ergosterol and 24,(28) dehydroergosterol, the latter is not found in any of the mutants whilst ergosterol is lacking in pol 2 and only present at very low levels in pol 3. The spectra of extracts of pol 1 and pol 3 indicate the presence of new sterols (Woods, 1971). Mutants of pol 1 excrete sterol into the growth medium. Studies on double mutants indicate epistasis between pol genes with respect to sterol pattern and suggest that they are metabolically related in the sequence pol 2 → pol 3 → pol 5 → pol 1 → pol 4 → pol +. A rapid qualitative technique for the preparation of non-saponifiable extracts of yeast for sterol analysis is described.

Release of Protoplasts from Schizophyllum commune by a Lytic Enzyme Preparation from Trichoderma viride

Abstract: SUMMARY: Spherical, osmotically sensitive protoplasts were liberated from the mycelium of Schizophyllum commune through the action of an extracellular enzyme preparation from the culture filtrate of Trichoderma viride grown on hyphal walls of the former organism. The conditions for obtaining stable protoplasts were determined. Maximum numbers of protoplasts were released from young growing mycelium by using MgSO4 or KCI at an osmotic potential between —12.8 and —17.8 atm in the presence of 0.05 M-maleic acid-NaOH at pH 5.8. Protoplasts were released through ruptures in the wall, initially at the apices, but later also from older parts of the hyphae.

The Bursting Tendency of Hyphal Tips of Fungi: Presumptive Evidence for a Delicate Balance between Wall Synthesis and Wall Lysis in Apical Growth

Abstract: SUMMARY: A wide diversity of treatments can cause rapid and extensive bursting of hyphal tips of Mucor rouxii. Most hyphal tips from colonies grown on full-strength agar medium burst readily when flooded with distilled water. In contrast, hyphal tips from colonies grown on diluted medium survived flooding with distilled water but succumbed to dilute aqueous solutions (particularly acids, but also neutral salts, EDTA, alcohols, acetone, detergents). Apex bursting was generally inhibited by alkaline solutions but took place at certain concentrations of ethanolamine or NH40OH. Mg2+, Mn2+ or Ca2+ caused pronounced swelling of the hyphal apex followed by an occasional burst. Sharp temperature increases also brought about apical disintegration regardless of nutrient concentration. Colonies of Aspergillus fumigatus, Fusarium sp., Neurospora crassa (wild-type and two morphological mutants), Penicillium claviforme, Rhizoctonia solani and Rhizopus arrhizus also underwent apical bursting when flooded with water or rapidly heated. Schizophyllum commune, several Phytophthora spp., and some morphological mutants of N. crassa were refractory. The bursting of hyphal tips by flooding colonies with water is not simply an osmotic phenomenon; its temperature coefficient (Q10 1.3 to 2.0) suggests the additional participation of biochemical reaction(s) as a rate-limiting step in the bursting process. Probably, enzymatic degradation and hence weakening of the wall is a prerequisite for bursting. These observations are offered as circumstantial evidence supporting the following conclusions: (i) the growing tips of fungi have a large wall lytic potential; (ii) the release of this activity during growth must be gradual and delicately co-ordinated with wall synthesis; (iii) this balance can be easily disturbed by a wide variety of external stimuli and the ensuing surge of lytic activity results in the violent disintegration of the hyphal apex.

Shortening of Pseudomonas aeruginosa pili after RNA-phage adsorption.

Abstract: SUMMARY: The F-pilus retraction theory suggests that F-pili retract on contact with a recipient bacterium or pilus-specific bacteriophage, but there has been no direct demonstration of any form of pilus retraction. Electron microscopy is used here to study average length changes in Pseudomonas aeruginosa RNA-phage pili after the adsorption of RNA-phage virions to the sides. The theory predicts that, if one phage per pilus is adsorbed, there should be a reduction of about 50% in the mean length due to the adsorption of virions at random points; retraction would be stopped at the point of adsorption when the virus reached the bacterial surface. A phage-resistant, pilus-bearing P. aeruginosa strain (PAO68), used as a control, showed no such change. The phage-sensitive strain PAOI showed an average reduction in pilus length of about 42.5% relative to its length before adsorption, or 50% relative to the PAO68 average. This strongly suggests pilus retraction in PAOI but not in PAO68. In electron micrographs, phage virions are seen almost always at the bases of PAOI pili, whereas virions adsorbed to PAO68 are randomly distributed along the pili.

Ammonium Repression of Extracellular Protease in Aspergillus nidulans

Abstract: Summary: Extracellular protease of Aspergillus nidulans is repressible by ammonium. A mutant (xpr D i) selected for derepression of protease in the presence of ammonium is also derepressed for nitrate reductase, xanthine dehydrogenase and glutamate uptake; it retains the ability to use ammonium as sole nitrogen source. The mutant is partially dominant in heterozygous diploids. The mutation does not confer methyl-amine resistance, nor are methylamine-resistant (meaA) strains derepressed for protease.

Flagellum mutants of Chlamydomonas reinhardii.

Abstract: Summary: Mutants blocked in different stages of flagellar development were isolated and examined by light and electron microscopy. Flagellum-less mutants had normal basal bodies but lacked the flagellar shaft and showed abnormalities in the transitional region. Stumpy mutants had very short flagellar shafts in which electrondense material, sometimes arranged in sheet-like arrays, accumulated in the space between the outer tubules and the distended flagellar membrane. Short-flagellum mutants also showed abnormalities in the flagellar shaft; abnormally spaced radial spokes were seen in negatively stained frayed flagella of one of these mutants. The flagellum lengths and flagellar regeneration characteristics of two long-flagellum mutants with defective length control were determined; length was highly variable with some abnormally long flagella, and regeneration was slow and asynchronous.

The Taxonomy of the Crown-gall Organism Agrobaterium tumefaciens and Its Relationship to Rhizobia and Other Agrobacteria

Abstract: SUMMARY: Strains of agrobacteria, rhizobia and other organisms were collected from various sources and tested for their ability to utilize 61 compounds as sole carbon sources, oxidative or fermentative glucose metabolism, hydrolysis of starch, casein and gelatin, anaerobic arginine metabolism and production of 3-ketolactose. The resulting data was used in a numerical analysis and the strains were grouped on the basis of overall similarity. The resultant groupings confirmed the idea that the genera Agrobacterium and Rhizobium be combined, and four species of fast-growing rhizobia were recognized: Group I, Rhizobium radiobacter; Group II, Rhizobium meliloti; Group III, related to Agrobacterium rhizogenes and the Biotype 2 strains of Keane, Kerr & New (1970); Group IV, Rhizobium leguminosarum. Crown-gall organisms were associated with groups I and III. The four species were defined without reference to pathogenicity or nodulating ability and it appears at present that crown-gall organisms can only be distinguished by pathogenicity testing. Agrobacterium rubi H36 probably belongs in the genus Rhizobium whereas Agrobacterium gypsophilae 1948 and Agrobacterium pseudotsugae 180 do not.

Wall replication in saccharomyces species: use of fluorescein-conjugated concanavalin A to reveal the site of mannan insertion.

Abstract: SUMMARY: The wall mannan in dividing Saccharomyces cells was labelled by exposing the yeasts to fluorescein-conjugated concanavalin A. The yeasts were then allowed to grow in the absence of excess staining reagent and were examined by fluorescence microscopy at several intervals after the re-initiation of growth. The newly synthesized mannan was non-fluorescent and, thus, could be easily distinguished from the material present at the outset. Most new mannan was deposited in the wall surrounding the bud, and little if any of the mannan in the bud wall was derived from the surface of the mother cell. Deposition of new mannan in the mother cell was detected only in the bud scar. The distal tip of the growing bud was identified as the major site at which new mannan was inserted into the existing wall fabric. This area is also known to be the deposition site of newly synthesized glucan. Thus, with respect to these two major wall polysaccharides, wall replication in Saccharomyces cells resembles the apical mode exhibited by filamentous fungi.

Inhibition of Mucor rouxii by Polyoxin D: Effects on Chitin Synthetase and Morphological Development

Abstract: Summary: Polyoxin D is a strong inhibitor of growth and spore germination of Mucor rouxii. This antibiotic inhibited the growth of both the yeast and mycelial forms of M. rouxii. It caused some minor morphological alterations but did not decisively affect the pattern of dimorphic development. Polyoxin D is a powerful competitive inhibitor of chitin synthetase (K i, = 0·6 μm). Organisms growing at inhibitory concentrations of the antibiotic exhibited weakened walls that were susceptible to bursting.

A Chemostat Study of the Effect of Fixed Nitrogen Sources on Nitrogen Fixation, Membranes and Free Amino Acids in Azotobacter chroococcum

Abstract: SUMMARY: Increasing concentrations of ammonium ions in the medium of nitrogen-fixing, sulphate-limited continuous cultures of Azotobacter chroococcum caused a proportionate repression of nitrogenase activity; free NH4 + could be detected in the extracellular culture fluid only when nitrogenase activity was wholly repressed. The NH4 + concentrations giving 50% or 100% repression were proportional to the population density. Nitrate ions repressed with similar stoichiometry; glutamate, glutamine and aspartate did not repress and were not metabolized; repressed and derepressed populations contained equal amounts and proportions of glutamate-forming enzymes. Repressed populations lacked both enzymatic components of nitrogenase. The intracellular free amino acid pools were typical of Gram-negative bacteria; an increase in the degree of repression was associated with an increase in the pool levels of ammonia, aspartate and glutamate. Nitrogen-fixing populations possessed a convoluted intracytoplasmic membrane system which was absent from ammonia-assimilating organisms, but the phospholipid contents of the two types of population were similar. All members of a half-repressed population possessed these membranes, but to a lesser extent that fully derepressed populations. When N2-fixing chemostat populations were abruptly exposed to repressive concentrations of ammonium succinate. repression occurred exponentially and nitrogenase activity disappeared from the culture faster than wash-out of stable enzyme. Repression was not alleviated by exogenous cyclic AMP. Derepression was complete, according to the acetylene test, within half a doubling time of disappearance of free ammonium ions from the culture.

A taxonomic study of some coryneform bacteria.

Abstract: Summary: Numerical analysis has been carried out on 110 features of 158 named and unnamed coryneform bacteria. At the 30 % S-level, four phena of unequal size were formed, the largest of which (phenon II) was divided into two subphena at the 45 % S-level representing the genera Arthrobacter and Nocardia. Phenon III was divided into two subphena at the 45 % S-level (III A and IIIB). Subphenon IIIA was made up largely of Gram-positive strains received as Flavobacterium. Subphenon IIIB contained a variety of strains including a group of cellulomonas-like organisms. Phenon IV was divided into two subphena at the 35 % S-level representing the animal-pathogenic corynebacteria and Microbacterium flavum respectively. Phenon V contained six strains of which five were plant pathogenic corynebacteria. DNA base composition determinations were carried out on representative strains and the values obtained generally correlated well with the numerical groupings. Considerable reorganization of most coryneform genera was considered necessary and suggestions for the reclassification of species and of particular strains have been made.

Two Modes of ‘Curing’ Transmissible Bacterial Plasmids

Abstract: SUMMARY: F'lac was efficiently eliminated by acridine orange from Escherichia coli K12, whether sex pilus synthesis was constitutive or repressed by an fi +R factor. R factors, F-like or I-like, repressed or derepressed. were not eliminated by acridine orange. Sodium dodecyl sulphate (SDS), known to eliminate certain plasmids determining constitutive synthesis of F pili, had no effect on cultures with wild-type (repressed) R factors. Bacteria with derepressed synthesis of pili, either F-like or I-like, but particularly the latter, showed increased sensitivity to SDS. SDS treatment selected from such cultures non-piliated cells, with lost or mutant R factors. Thus acridine orange was a true ‘curing’ agent, specific for F, whilst SDS acted only by selection of spontaneous variants.

Antimicrobial Properties of Cytochalasins and Their Alteration of Fungal Morphology

Abstract: Summary: Cytochalasin A inhibited growth of Bacillus subtilis and Escherichia coli and increased motility of the latter. Both cytochalasins A and D have antifungal properties, inducing branching and, at higher concentrations, swelling of hyphal tips in Botrytis cinerea. Cytochalasin B showed neither antibacterial nor antifungal activity. The observed antimicrobial effects of cytochalasins A and D are discussed in relation to those of related antibiotics.

Continuous culture studies on the biosynthesis of alkaline protease, neutral protease and -amylase by Bacillus subtilis NRRL-B3411.

Abstract: SUMMARY: The amounts of three catabolite repressible enzymes, alkaline protease, neutral protease and α-amylase, produced by Bacillus subtilis NRRL-B3411 growing in a chemostat, depended on the growth-limiting substrate. Limiting growth with glucose was advantageous for α-amylase synthesis while nitrogen-limited growth was advantageous for synthesis of the two proteases. Under the conditions used, continuous cultures were unsuitable for large-scale production of the three enzymes since spontaneous mutations to less productive strains occurred in the long term.

Fatty Acid Distribution in Triglycerides of Yeasts Grown on Glucose or n-Alkanes

Abstract: SUMMARY: Lipid contents of yeasts grown on glucose were: Candida lipolytica, 5.4%; C. tropicalis, 9.4%; C. utilis, 2.7%; Candida 107, 41%; Hansenula anomala, 12.5%; Rhodotorula glutinis, 2.7%; and R. graminis, 9.1%. In each yeast about 80% of the lipid consisted of triglycerides. When the triglycerides from five of the yeasts were analysed in detail, an unsaturated acid was invariably found at the 2-position. With Candida 107 and R. graminis about 50% of the total triglyceride fatty acids were saturated, resulting in over 50% of the triglycerides being of the 1,3-disaturated-2-monounsaturated type. When Candida 107 and C. tropicalis were grown on individual n-alkanes, from C12 to C16, the fatty-acid composition varied according to the chain length of the substrate, although with n-tridecane neither yeast produced tridecanoic acid in the triglyceride and with n-dodecane only C. tropicalis contained an appreciable amount of dodecanoic acid in the triglyceride (32% of the fatty acids). With both yeasts on each alkane substrate, the lipid contents were not only lower than when grown on glucose but contained a smaller proportion of triglyceride. Saturated acids were now located at the 2-position of the triglycerides: Candida 107 grown on n-tetradecane produced 46% of its triglycerides with a saturated acid at the 2-position. The main advantage to be gained by growing yeasts on n-alkanes is, as far as lipid formation is concerned, the biosynthesis of specific fatty acids rather than the production of plant-like triglycerides.