The capacity of Pseudomonas putida PpG7 (ATCC 17,485) to grow on naphthalene, phenotype Nah+, is lost spontaneously, and the frequency is increased by treatment with mitomycin C. The Nah+ growth character can be transferred to cured or heterologous fluorescent pseudomonads lacking this capacity by conjugation, or between phage pfl6-sensitive strains by transduction. After mutagenesis, strains can be selected with increased donor capacity in conjugation. Clones which use naphthalene grow on salicylate and carry catechol 2, 3-oxygenase, the initial enzyme of the aromatic a-keto acid pathway, whereas cured strains grow neither on salicylate nor naphthalene and lack catechol 2, 3-oxygenase, but retain catechol 1, 2-oxygenase and the aromatic ,8-keto adipate pathway enzymes.

Different aspects of stress response of Lactobacillus acidophilus were investigated. First, the sublethal and lethal levels of bile, heat, and NaCl stresses were determined. They were 0.05% and 0.5% (bile), 53 degrees C and 60 degrees C (heat), and 2% and 18% (NaCl), respectively. To evaluate the effect of each stress at log phase, log-phase cultures were challenged directly with the lethal level of each stress (control) and were compared to log-phase cultures that were pre-exposed to the sublethal level prior to the exposure at the lethal level (test). Some, if not most, of the cells were killed in the control cultures against each of the three stresses. However, in the test cultures, the number of cells that had survived increased significantly. It appears that L. acidophilus is capable of displaying adaptive response to stress. The adaptive response to one stress was also shown to provide cross-protection against different stresses tested. The effect of each stress on stationary-phase cultures was also investigated. In contrast to log-phase culture, stationary-phase culture was inherently resistant to stress.

The kinetics of nisin production was studied in batch cultures using a construct of Lactococcus lactis subsp. lactis C2SmPrt-, containing a transposon (TnNip) that encodes nisin production. The introduction of TnNip into C2SmPrt- significantly lowered the specific growth rate and the maximum A620 reached was reduced from 15.2 to 11.0. The effect of nisin concentration and nutrient depletion on nisin production of the construct, C2SmPrt-(TnNip), was examined. Nisin production was found to be inhibited by high concentrations of nisin, when grown in excess nutrient, even though growth of the culture continued because nutrient limitation was not operating. However, in low nutrient concentrations nisin production was limited by nutrient depletion. The specific growth rate of C2SmPrt-(TnNip) was altered, by using different nutrient concentrations and different sugars, in order to examine the relationship between nisin production and growth. Nisin production was shown to be growth-associated for most of growth, but near the end of growth, when the specific growth rate was 0.05 h-1 or less, the production ceased.

SUMMARYPseudomonas arvillamt-2 (ATCC 23073) has been shown to harbour a transmissible plasmid which codes for the degradation of benzoate andm-toluate. Plasmid-borne genetic information codes for the conversion of these compounds to catechol then the assimilation of catechol via themetacleavage pathway.

When Lactic Acid Bacterial cultures were frozen at -20 degrees C for 24 h, the cell viability decreased drastically, but when they were cold shocked at 10 degrees C for 2 h prior to freezing, viability improved significantly for the Lactococcus lactis subsp. lactis strains (25-37%) and Pediococcus pentosaceus PO2 (18%), but not for the Lactococcus lactis subsp. cremoris strains tested or for one strain of Lactobacillus helveticus LB1 and Streptococcus thermophilus TS2. When the period for cold shock was extended to 5 h, the viability increased even further for those strains that displayed cold shock cryotolerance. Use of degenerate PCR primers based on the major cold shock protein (csp) of both Escherichia coli and Bacillus subtilis resulted in PCR products from all strains tested. The PCR product from Lactococcus lactis ssp. lactis M474 was cloned and sequenced, and the deduced amino acid sequence displayed a high sequence similarity to other csp's. Use of PCR primers based on the M474 sequence resulted in PCR products being produced only from the lactococcal strains studied and not from the Lactobacillus helveticus, Streptococcus thermophilus, or Pediococcus pentosaceus strains tested.