The predictive local composition model is applied to multicomponent hydrocarbon systems with long-chain n-alkanes as solutes. The results show that it can successfully be extended to high-order systems and accurately predict the solid appearance temperature, also known as cloud point, in solutions of known composition using only binary information. The model can describe the experimentally well-known capacity of heavy alkanes to act as cloud-point depressants and explains it in terms of the nonideality of the solid solutions formed. There are good indications that no significant error is introduced by considering the multiple orthorhombic phases as a single phase. It is shown that for low concentrations in heavy fraction the interaction parameter αls can be neglected and thus the model becomes purely predictive.

No abstract

No abstract

The temperate lactococcal phage TP901-1, induced by UV light from Lactococcus lactis subsp. cremoris 901-1, was characterized. The restriction map was found to be circular, and the packaging of TP901-1 DNA was concluded to occur by a headful mechanism. The pac region was localized on the 38.4-kb phage genome. TP901-1 belongs to the class of P335 phages (V. Braun, S. Hertwig, H. Neve, A. Geis, and M. Teuber, J. Gen. Microbiol. 135:2551-2560, 1989. Evidence is presented that the phages TP936-1 (V. Braun, S. Hertwig, H. Neve, A. Geis, and M. Teuber, J. Gen. Microbiol. 135:2551-2560, 1989) and C3-T1 (A. W. Jarvis, V. R. Parker, and M. B. Bianchin, Can. J. Microbiol. 38:398404, 1992) are very closely related to or are identical to TP901-1. The lytically propagated TP901-1 phages were able to lysogenize both indicator strains Lactococcus cremoris 3107 and Wg2. Lysogenization resulted in site-specific integration of the phage genome into the bacterial chromosome. Only one chromosomal attB site was found in 20 independent lysogens. The attP region of TP901-1 and the attL and attR regions were cloned and sequenced. The results showed a core region of only 5 bp, in which the recombination occurs, followed after a 1-bp mismatch by a 7-bp identical region, TCAAT(T/C)AAGGTAA. This result was further verified by sequencing of the attB region obtained by PCR. An integration vector was constructed with the 6.5-kb EcoRl fragment from TP901-1 containing attP. This vector also functions in the plasmid-free strains MG1363 and LM0230 with only one specific attB site, strongly indicating a more general use of the TP901-1-based integration vector in lactococci. In this report, we present the restriction map of phage TP901-1, including the location of the attP andpac regions. We have been able to monitor the lysogenic life cycle of the phage and demonstrate the presence of only one major attachment site. An integration vector based on TP901-1 DNA sequences was constructed, and the attP, attL, attR, and attB regions were identified, cloned, and sequenced. The integration system from TP901-1 was also shown to be functional and site specific in the laboratory strains often used for genetic studies of lactococci, namely Lactococcus lactis subsp. lactis MG1363 and LM0230. This strongly indicates that the integration system of TP901-1 may be of general use as a genetic tool with lactococci. MATERIALS AND METHODSBacteria, plasmids, and phages. Bacterial strains and plasmids used in this work are listed in Table 1. Phage DNA from phages C3-T1 (13) and XLC3 (22) Temperate phages were induced from their hosts by UV irradiation. M17 broth was inoculated with 1% (vol/vol) of an overnight culture of the lysogenic strain. The culture was at an optical density at 600 nm of 0.15, harvested at 5,000 x g for 10 min, and resuspended in 0.5 volume of NC (0.5% NaCl [wt/vol], 5 mM CaCl2). The suspension was pumped through a quartz flow cuvette placed at the bottom of a UV field (254 1069

No abstract