- Volume 112, Issue 2, 1979

SUMMARY: From a strain of Bacillus stear othermophilus, devoid of active pyruvate carboxylase, a mutant (NG-15) was selected that grew on acetate in the presence of glucose. This mutant differed from its parent organism in possessing high activities of isocitrate lyase when grown on all carbon sources tested except nutrient broth, in possessing unusually low activities of NADP+-dependent isocitrate dehydrogenase and in containing increased amounts of isocitrate. Revertants of mutant NG-15 which regained the ability to synthesize active pyruvate carboxylase also synthesized isocitrate lyase and isocitrate dehydrogenase to the same extent as the wild-type strain. These results suggest that the regulatory mechanism for the synthesis of isocitrate lyase in the thermophile may be different from that in mesophilic bacilli.

SUMMARY: Cytophaga johnsonae and C. aquatilis (ATCC 29551), examined by frozen-surface replica and freeze-etch techniques, displayed undulated and particulated surfaces. They produced copious amounts of extracellular slime when cultured. Cytophaga aquatilis contained large, complex mesosomes in freeze-etched cells whereas C. johnsonae contained none. In non-cryoprotected freeze-etch preparations, C. aquatilis contained two major fracture planes whereas the C. johnsonae cell envelope fractured in three distinct planes. Linear fibres, such as the peripheral fibrils previously described in Flexibacter columnaris, were not observed in the outer membrane of freeze-etched C. aquatilis. Cytophaga johnsonae contained periplasmic linear fibrils; however, these appeared to be associated with the outer surface of the cytoplasmic membrane or an intermediate layer and not with peripheral fibrils.

SUMMARY: A freshwater Spirillum sp., which apparently belongs to a niche of low nutritional status (Matin & Veldkamp, 1978 ), accumulated poly-β-hydroxybutyric acid (PHB) during lactate-limited growth in continuous culture. The PHB content varied in a complex manner with the dilution rate (D), but was greatest at the lowest D value examined: about 18% (w/w) at D = 0.025 h−1. It is not known what mechanism accounted for PHB accumulation during carbon-limited growth. The resistance of cultures of Spirillum sp. to starvation after growth at various D values was compared with that of a Pseudomonas sp. which appears to belong to relatively richer environments (Matin & Veldkamp, 1978 ) and does not accumulate PHB. In Spirillum sp., resistance correlated directly with the PHB content of the culture subjected to starvation, whereas in Pseudomonas sp. it increased with RNA content. Further, after growth at D = 0·03 to 0·05 h−1, the Spirillum sp. was much more resistant to starvation than was the Pseudomonas sp. Since the microflora of oligotrophic environments are probably often subjected to starvation conditions, PHB accumulation by Spirillum sp. during growth in such environments may assist survival. PHB in Spirillum sp. was rapidly degraded during starvation but it had no sparing effect on RNA degradation. It is not known how PHB enhanced resistance to starvation.

SUMMARY: The production of fimbriate (Fim+) recombinants was observed in transductional crosses between different pairs of wild-type strains of different biotypes of Salmonella typhimurium. Fim+ recombinants were readily produced in transductions from Fim+ donor strains to Fim− recipient strains and, less frequently, between some pairs of Fim− strains, for example, between almost any strain of the FIRN biogroup (Fim− Inl− Rha− Bxyl−) and many strains of the non-FIRN Fim− biogroup. None of numerous crosses between different pairs of FIRN strains gave Fim+ recombinants, suggesting that the fim mutation was present at the same intragenic site in all FIRN strains. FIRN strains are thought to have descended from a single ancestral FIRN bacterium which originated by a series of mutations from a strain of the common biotype la (Fim+ Inl+ Rha+ Bxyl+). Two FIRN-like (Fim− Inl+ Rha− Bxyl−) strains that did not yield Fim+ recombinants in crosses with FIRN strains were probably wild-type Inl+ mutants from FIRN strains.

SUMMARY: A Bacillus subtilis mutant which formed dark-brown ‘medusa’ (M) colonies was obtained. It sporulated at a high frequency, overproduced extracellular protease during sporulation and possessed a high genetic instability with a complex segregation pattern. Segregation was maintained after repeated re-isolation of single M colonies. The major wild-type-like class of segregants (B) was stable, sporulated normally and produced normal amounts of protease. Occasionally segregants were obtained which produced extremely high amounts of protease, sporulated poorly, formed transparent colonies and were either highly unstable (TD) or stable (TDst). Rarely B(D) (stable, normal sporulation and protease overproduction) and W and T (both stable and asporogenous) segregants were produced. The M phenotype was transmitted as a single factor by transformation but not by transduction. The results of transduction experiments suggest the presence of two mutations, ScoC and ScoD. It is proposed that this new segregating system in B. subtilis may result from tandem duplication of part of the bacterial chromosome.

SUMMARY: In the genetically unstable, protease-overproducing ‘medusa’ (M) strains of Bacillus subtilis, segregation of stable, wild-type-like B cells occurred mainly during sporulation. After the end of the exponential growth phase, a small fraction of M cells sporulated quickly and formed M spores, while the majority of the cells, after a ‘critical period’, gave rise to B segregants which sporulated after a delay. Segregation occurred without cell division. Delayed sporulation, segregation and protease overproduction are related. Similar but more complex results were obtained with the highly unstable TD strains. Sporulation and the kinetics of protease overproduction were also followed in several stable segregants. Depending on the strain, either the rate of protease production or both the rate and time course were affected. The results are interpreted in terms of sequential activation and de-activation of sporulation genes. The production of the alkaline and the neutral proteases was, in general, under common genetic control. In some strains α-amylase was also overproduced.

SUMMARY: Bacteriophage C5 of Pseudomonas aeruginosa is able to reactivate ultraviolet (u.v.)-irradiated phage E79 in coinfection experiments and decrease the u.v.-sensitivity of a host-cell reactivation deficient mutant. These properties suggest that phage C5 has a gene(s) which is involved in the repair of u.v.-damaged DNA. The isolation of two u.v.-sensitive mutants of C5 supports this hypothesis.

SUMMARY: Trimethylamine oxide (TMAO) stimulated both the anaerobic growth rate and the growth yield of Proteus NTHC 153. The molar growth yield from glucose and pyruvate in tryptone/ yeast extract medium doubled in the presence of TMAO, and the organism grew anaerobically on the non-fermentable substrates l-lactate and formate when TMAO was added to the medium. We conclude that TMAO stimulated growth by serving as a terminal electron acceptor in an oxidative phosphorylation process.

SUMMARY: Common type 1 fimbriae were isolated from Escherichia coli and their length distribution profile was determined before and after treatment with ultrasound. As fimbriae were shortened, so their haemagglutinating capacity decreased, but their ability to bind to erythrocytes did not decrease to the same extent. Isolated fimbriae did not agglutinate inside-out vesicles prepared from horse erythrocytes or liposomes, suggesting that the binding mechanism was not based on non-specific hydrophobic interactions. The results support a lateral rather than a terminal location for the fimbrial binding site responsible for haemagglutination.

SUMMARY: Phosphoglycerate phosphomutase of Bacillus subtilis, Bacillus cereus and Bacillus megaterium required Mn2+ as cofactor, whereas the wheat germ and rabbit liver enzymes did not. In the absence of Mn2+, B. subtilis did not sporulate in normal sporulation media but it did sporulate if the proper ratio of glucose or glycerol and malate was used. Decoyinine, an inhibitor of guanosine monophosphate synthesis, induced sporulation in the presence of excess glucose and malate to the same extent with and without Mn2+. Apparently, phosphoglycerate phosphomutase is the only strictly Mn2+-requiring enzyme needed for optimal sporulation in normal sporulation media.

SUMMARY: The free-swimming ciliate Paramecium avoids warm regions. We have developed a quantitative assay of thermal avoidance, based on the interference between thermal avoidance and the normal tendency to swim upward (negative geotaxis). Paramecium tetraurelia swimming in a Tris/Ca2+ solution avoided a region warmer than about 40°C. Several factors influenced the strength of the response, including the concentrations of monovalent cations and Ca2+, the temperature of the test region, and the temperature at which the animals had been cultured. At 1 mm-Ca2+, increasing Na+ concentration enhanced avoidance of a 40°C region, and at a constant Na+ concentration (0·5 mm), avoidance improved with decreased Ca2+. When the ratio [Na+]/[Ca2+]1/2 was held constant, varying Na+ and Ca2+ concentrations did not affect thermal avoidance. Other monovalent cations (Cs+, Li+, Rb+) and hydroxylamine also enhanced thermal avoidance, and K+ was somewhat less effective than these. The strength of the avoidance response increased with increasing test temperature in the range of 37 to 42°C for cells grown at 28°C. Cells grown at 15°C had a lower threshold for thermal avoidance, and those grown at 35°C showed no avoidance at 40°C and only poor avoidance at higher temperatures. Cells cultured at 15 or 35°C and then shifted to 28°C acquired the thermal behaviour typical of cells cultured at 28°C. Behavioural mutants with defective Ca2+ channels (Pawns) are incapable of reversing their swimming direction and showed little or no thermal avoidance. We suggest that thermal avoidance is triggered by thermotropic phase transitions in the lipids of the excitable membrane of Paramecium tetraurelia.

SUMMARY: A synthetic medium containing inorganic sources of N, P, Fe, S, Ca2+ and Mg2+, trace minerals and essential vitamins was developed for anaerobic degradation of cellulose to CH4. A mixed culture obtained from sewage sludge and grown in batch culture in this medium degraded about 4 g cellulose l−1 week−1 and produced about 710 ml total gas per g cellulose degraded. The gas produced contained between 51 and 56% CH4, the remainder being CO2. For maximum degradation of cellulose to CH4 and CO2, the requirement for essential salts other than HCO3 −, Fe and S2- was comparable to that of other anaerobes. NH4 + or Na2CO3 at 20 to 24 mm and total Fe at 0·4 to 0·6 mm gave optimum conversion of cellulose to CH4, while the inclusion of additional S2- in the presence of 1·75 mm-SO4 2- was not required.

SUMMARY: At dissolved oxygen tensions of 15 mmHg (2 kPa) and below, nitrate-limited continuous cultures of Klebsiella K312 synthesized nitrate reductase (NR) and nitrite reductase (NiR) and excreted ammonia. Under anaerobic conditions over 60% of the nitrate-nitrogen utilized was excreted as ammonia. In contrast, carbon-limited cultures excreted nitrite at dissolved oxygen tensions of 15 mmHg or below and synthesized NR but not NiR. Ammonia repressed neither NR nor NiR synthesis. These observations indicate that below a critical oxygen tension of 15 mmHg Klebsiella K312 utilizes oxygen and nitrate as electron acceptors. This oxygen tension correlates well with the critical oxygen tension observed for a change from oxidative to fermentative metabolism in cultures of Klebsiella aerogenes. The product of dissimilatory nitrate reduction is ammonia in nitrate-limited cultures but principally nitrite in carbon-limited (nitrate excess) cultures.

SUMMARY: Good synchronous cultures of the fission yeast Schizosaccharomyces pombe can be made by selecting small cells from the Beckman JE-6 elutriator rotor. More important, the rate of leucine incorporation in controls shows far less perturbation than after selection from tube gradients. Elutriation may therefore be the best available method for reducing perturbations in selection synchronized cultures.