The new small cryptic plasmid pNMO propagating in Lactobacillus casei IAM 1045 was isolated from a naturally occurring Lactobacillus strain N1f. Sequencing analysis revealed that the pNMO genome is a double-stranded DNA of 3522bp, and has two possible open reading frames, rep and pre as well as three other minor ORFs. The predicted rep product (Rep) of 318 amino acids bears close resemblance to other presumed replication proteins (Rep) encoded by the Lactobacillus plasmids such as pLP1, replicating by the rolling-circle (RC) mechanism via single-stranded (SS) DNA intermediates. Upstream rep, pNMO carries two putative replication origins: one is a Rep-mediated nick-site for the plus-strand synthesis (+ori), and the other is a single strand origin (sso) for the minus-strand replication. Preliminary in vivo experiments suggested that pNMO generates SS DNA intermediates in the N1f cells. On the other hand, the putative pNMO pre product (Pre) of 361 amino acids shows extensive similarity to other presumed Pre/Mov (plasmid recombination/ mobilization) proteins encoded by the Lactobacillus plasmids pLB4 and pLAB1000. These results suggested that pNMO replicates via the RC mechanism, and carries the Pre/Mov system.
Distribution of a Tween-hydrolyzing esterase in the genus Acidiphilium was investigated using 40 strains. The strains were divided into three groups by the cell growth and productivity of extracellular esterase. Only the strains referred to as A. facilis cluster produced a large amount of the esterase in the culture broth. The esterase was inductively produced by adding polyoxyethylene sorbitan acyl esters or sorbitan acyl esters as carbon source, but not by adding polyoxyethylene alkyl ethers or triacylglycerols. Acidiphilium sp. AIU 409 isolated from a strong acid mine drainage showed maximum esterase productivity in the medium containing 1.0% Tween 80 at pH 3.5. The extracellular and cell-bound esterases from strain AIU 409 hydrolyzed polyoxyethylene sorbitan acyl esters and sorbitan acyl esters, but not triacylglycerols. The esterase produced by strains of A. facilis cluster might be a new lipolytic enzyme.
Saccharomyces cerevisiae was grown on different concentrations of sucrose and glucose mixtures after adapting on sucrose. The yeast cells were found to have two different mechanisms by which sucrose was utilised: hydrolysis outside the cell membrane and direct transport into the cells. The mechanism by which sucrose was utilised depended on the initial concentration of glucose in the mixture and the adaptation state of the cells. In both cases, glucose was utilised first and invertase secretion was repressed when the glucose concentration was higher than 2gl-1. The major important finding in our results is that, for fully sucrose-adapted cells, even in the presence of a repressive glucose concentration, the yeast cells were able to utilise sucrose, and most importantly, without first being hydrolysed to its constituent monosaccharides. Previously, it has been thought that direct transport of sucrose contributes only a small part of the process of utilisation of sucrose, but as our results indicate it can be the major mechanism of sucrose utilisation in S. cerevisiae if the cells are adapted on sucrose for long periods, glucose concentrations in the medium are high and/or invertase activities are limiting.
A molecular karyotyping technique consisting of pulsed-field gel electrophoresis of intact chromosomal DNAs and following Southern hybridization with total HindIII-digested DNAs was used as a tool for yeast classification and identification. Significant differences in chromosomal patterns were found among 16 Saccharomyces exiguus strains. The complex taxon, classified into several groups of different karyotypes, showed a low degree of cross-DNA homology.
Bacillus carboniphilus strains under the ordinarily non-permissive stress of high KCl concentrations and high-temperature conditions are very sensitive recipients of growth-promoting signals from both homologous and heterologous bacterial cells. These signals are not due to a volatile chemical substance, but are of a physical nature, very probably sonic, since they can be transmitted from one Petri dish to another even through a 2mm iron barrier.