摘要:

A cold-sensitive (CS) mutant of the psychrotroph,Bacillus psychrophilus, was obtained byN-methyl-N′-nitro-N-nitrosoguanidine mutagenization and penicillin counterselection. In the presence of citrate, the wild type grew well at both 5 and 20 °C whereas the CS mutant grew well at 20 °C (the permissive temperature) but, at 5 °C (the restrictive temperature), grew at a reduced rate for two to three generations followed by a complete plateau in growth. Upon return of the CS mutant to 20 °C, after a delay of about 40 h, growth resumed at the appropriate rate. The CS mutant exhibited growth rates similar to parental rates on a wide variety of carbon sources at 5 °C, but when Krebs cycle intermediates were used as substrates and in the presence of an equimolar amount of citrate, the typical cold-sensitive growth pattern occurred. Comparison of oxidative phosphorylation in the parent and CS mutant indicated that no phosphorylation occurred at 5 °C in the CS mutant during the plateau in growth. Examination of the effect of temperature on ATPase activity showed that at 5 °C the specific activity of ATPase isolated from the CS mutant grown at 5 °C was 15-fold less than the ATPases isolated from wild-type cells grown at either 5 or 20 °C and 10.5-fold lower than ATPase from CS mutant cells grown at 20 °C. The large reduction in CS mutant ATPase activity at 5 °C appears to be at least partly due to an effect on synthesis since citrate did not inhibit preformed ATPase.

ISSN:0008-4166    

DOI:10.1139/m80-001

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Salmonella typhimuriummutants sensitive to coliphage P1 are resistant to salmonella phage P22 and lose their P1-sensitivity upon reversion to P22-sensitivity. A tryptophan-requiringSalmonella typhosa–Escherichia colihybrid, which has the unique ability to serve as recipient in transduction mediated by both P22 and P1, was used to determine if P22 and P1 adsorb at the same oroverlapping sites: (i) The adsorption of each of P1 and P22 is similar when added individually or together to the hybrid at a saturating multiplicity of infection (moi), (ii) P1 grown ontrp+E.coliyields the maximum frequency of Trp+abortive transductions at an moi of 6 with thetrphybrid recipient; the presence of increasing numbers of P22 grown ontrp S.typhimriumdoes not decrease the number of Trp+transduction from P1. (iii) A mixture of P1 (grown ontrp+E.coli) and P22 (grown ontrp+S.typhimurium) yields more abortive transductions than does P1 alone. Thus phages P1 and P22 adsorb to the hybrid cells on different sites.

ISSN:0008-4166    

DOI:10.1139/m80-002

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Strains isolated from disseminated gonococcal infections often require hypoxanthine for growth. The biochemical bases for the requirement for hypoxanthine in strains isolated from both disseminated (Ile−Val−Arg−Hyx−Ura−phenotype) and non-disseminated (Hyx−phenotype) infections were compared. The requirement for hypoxanthine was dependent upon the composition of the growth medium. In a complete defined medium, hypoxanthine was replaced by a mixture of adenine and guanine but not by either purine alone. The addition of adenine alone inhibited gonococcal growth. This inhibition was reversed by the addition of guanine and most likely resulted from an inhibition of de novo purine biosynthesis. In a histidine-free medium, adenine replaced the hypoxanthine requirement in Ile−Val−Arg−Hyx−Ura−strains. Adenine did not replace the hypoxanthine requirement in Hyx−strains. The Ile−Val−Arg−Hyx−Ura−strains exhibited a markedly reduced rate of de novo purine biosynthesis while Hyx−strains were blocked in this pathway. In vivo concentrations of purines are important factors which may limit the intracellular or extracellular growth of these strains.

ISSN:0008-4166    

DOI:10.1139/m80-003

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A reproducible and simple system for the production of germ tubes from yeast cells ofCandida albicansusing glucose and glutamine as substrates has been described.During germ tube formation there was a doubling of the dry weight but the number of cells remained constant. Although the DNA content did not change for the first 4 h of germ tube formation, the RNA content more than doubled. The DNA and RNA content ofC.albicansblastospores are 4.5 × 10−15 g per cell and 48 × 10−15 g per cell respectively.Nystatin, phenethyl alcohol, 2,4-dinitrophenol, azaserine, salicylhydroxamic acid, and 5-fluorocytosine were all effective inhibitors of germ tube formation. Cysteine, potassium cyanide, and polyoxin D did not prevent germination. The incorporation of both uracil and leucine occurred rapidly during germ tube formation. The inhibitors of RNA synthesis, actinomycin D, cordycepin, and daunomycin prevented germination and inhibited uracil incorporation. The translational inhibitors, trichodermin, aurin tricarboxylic acid, puromycin, and cyloheximide were effective in inhibiting both germ tube formation and leucine incorporation.

ISSN:0008-4166    

DOI:10.1139/m80-004

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Polluted river water was studied in an experimental lagoon to determine efficiency of removal of bacteriophages injected at the inlet of the lagoon. The bacteriophages were not significantly affected by the purification process and were found to migrate to the outlet in 4 to 5 days. They were detected 143 days after injection although about 80% of the added virus was removed by the lagoon treatment. These results contrast with those obtained withSalmonella, 99.9% of which were removed.

ISSN:0008-4166    

DOI:10.1139/m80-005

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Mycoplasma virus MVL 51, of the group L1 of Gourlay, has been shown to induce a chronic cell infection of two reference strains (1305/68 and JA 1) ofAcholeplasma laidlawii. Titers of virus and cells remain at a fairly high level during infection, around 108units/mL, with a mean ratio of approximately 1 PFU/1 CFU, as under control of a regulation mechanism. However, sudden spontaneous variations in the virus level do occur, from time to time, thus suggesting transient regulation breaks but not impairing the pattern of a more extensive regulation cycle.

ISSN:0008-4166    

DOI:10.1139/m80-006

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

WhenMycotypha poitrasii(Zygomycetes) is grown under standard conditions in liquid culture containing 1% polypeptone, 0.5% yeast extract, and variable glucose concentrations (0–6%), it displays mycelial–yeast conversion. "Intermediate" cells, isolated from cultures containing 2% glucose, are considered to represent a developmental phase in the process of morphogenesis. Distinct differences in the morphology and wall chemistry of the intermediate cells were demonstrated when compared to the yeast and hyphal forms. It is suggested that the trends evident from these comparative analyses reflect relationships between the alterations in cell wall chemistry and morphogenetic aspects of dimorphism.

ISSN:0008-4166    

DOI:10.1139/m80-007

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

NADP-specific malic enzyme (EC 1.1.1.40) has been purified about 160-fold from the moderate halophileVibrio costicola. The enzyme has a molecular weight of about 120 000. The purified enzyme was unstable in dilute solutions but could be stabilised by NaCl or glycerol. NH4Cl or KCl caused maximal activation at 0.1 M, but higher concentrations were inhibitory. NaCl did not activate and was instead a mixed-type inhibitor towards NH4Cl or KCl. The salt concentration affected the kinetic parameters of the reaction. The apparentKmforL-malate reached a minimal value at about 0.1 Msalt; the value for NADP, on the other hand, increased continuously with the salt concentration. The reaction also required a divalent cation activator, Mn2+being better than Co2+or Mg2+. NADH was a mixed-type inhibitor towards both substrates, whereas oxaloacetate was strictly competitive towards L-malate and non-competitive towards NADP. The inhibition kinetics were sigmoidal for NADH and hyperbolic for oxaloacetate. The malic enzyme fromV.costicolawas similar to those of a marinePseudomonasandHalobacterium cutirubrumin kinetic and regulatory properties but showed a response to salts intermediate between those of the latter enzymes.

ISSN:0008-4166    

DOI:10.1139/m80-008

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Cyclic adenosine 3′,5′-monophosphate (cAMP) activity was observed inStreptococcus lactisC2,Streptococcus cremorisC10,Streptococcus diacetlactis18-16, andStreptococcus thermophilusC3.In vitroassays of cell-free extracts obtained fromS.lactisC2 showed that the cAMP-associated enzymes adenyl cyclase and phosphodiesterase were also present.In vitroexperiments showed that prostaglandin E1(PGE) stimulation of adenyl cyclase increased cAMP concentrations approximately fivefold, andin vivostudies showed that PGE treatment ofS.lactisC2 increased intracellular cAMP concentrations twofold. Furthermore, PGE-induced elevation of intracellular cAMP levels was shown to prevent the repression of β-D-phosphogalactoside galactohydrolase synthesis by glucose.

ISSN:0008-4166    

DOI:10.1139/m80-009

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Candida utilisNRRL Y-900 was grown in aerobic continuous culture in a minimal salts medium with sucrose (1% w/v) as the carbon source. Increasing the concentration of zinc in the medium from 2.3 μMto about 30 μMresults in an increase in the apparent critical dilution rate from 0.3 to 0.47 h−1, and in the maximum biomass productivity from 1.5 g dry weight per litre per hour (atD = 0.33 h−1) to 2.56 g per litre per hour (atD = 0.45 h−1). The maximum steady-state level of cell-associated zinc (atD = 0.4 h−1) is 4 nmol Zn2+/mg dry weight, during carbon-limited growth, and about 9 nmol Zn2+/mg dry weight when FeCl3is omitted from the medium. At input zinc concentrations <20 μM, the cellular zinc concentration decreases linearly in proportion to the input zinc concentration and at <4.5 μMZn2+the culture becomes zinc-limited. Zinc-limitation results in a decrease in the growth yieldYsucrosefrom 0.54 to 0.38 g cells/g sucrose consumed, andY0from 22 to 13 g cells/g-atom O2, suggesting an altered efficiency of energy metabolism. The composition of the culture biomass with respect to protein and RNA content is not affected by zinc limitation.

ISSN:0008-4166    

DOI:10.1139/m80-010

出版商:NRC Research Press    

年代:1980

数据来源: NRC