Interactions between Pseudomonas aeruginosa and iodophor germicides in milking parlor udder wash water systems.

In a field study of 29 dairy farms, Pseudomonas aeruginosa was isolated more frequently (P = 0.05) from milking parlor udder wash water systems containing iodophor germicides than from those with no germicide. Most available iodine (AI2) concentrations were below the recommended level of 25 ppm (25 microgram/ml). Rubber and polyvinyl chloride hoses caused rapid decreases in the AI2 concentrations of 25 ppm iodophor solutions. AI2 dropped from 25 ppm to 6 ppm or less in 240 min for solutions contained in either polyvinyl chloride or rubber, compared with solutions in glass, which were unchanged in 240 min. Addition of inactivated iodophor solution to aqueous cultures resulted in significantly higher (P less than 0.05) numbers of P. aeruginosa at 10 and 24 h postinoculation. P. aeruginosa was grown in polyvinyl chloride tubing and exposed twice daily to 0, 10, or 25 ppm of AI2. None of the exposure concentrations eliminated the bacteria from the hoses, and bacterial numbers were not significantly different in hoses exposed to 0 and 10 ppm by the eighth treatment day. Bacteria taken from the water in these hoses were exposed to different concentrations of iodophor solution. Iodophor concentrations which will kill 50% of P. aeruginosa cultures previously exposed to 0, 10, and 25 ppm of AI2 were predicted to be 3.0, 11.8, and 20.8 ppm, respectively.     

Chromosomal rearrangements associated with morphological mutants provide a means for genetic variation of Candida albicans.

At frequencies as high as 1.4%, the pathogenic yeast Candida albicans spontaneously gave rise to morphological mutants exhibiting more than 20 different types of abnormal colonies; approximately two-thirds of the mutants were stable, while the other one-third were unstable and produced mixtures of different colonial forms at very high rates. Abnormal electrophoretic karyotypes were observed for all of the 14 mutants that were examined, indicating that they were associated with different types of single and multiple gross chromosomal rearrangements. Because C. albicans is asexual and does not go through a meiotic cycle, we suggest that the high frequency of chromosomal rearrangements provides a means for genetic variation in this organism.     

Molecular cloning of cDNAs derived from a novel human intestinal mucin gene

A human small intestinal lambda gt11 cDNA library was screened with antibodies to deglycosylated small intestinal mucin. Four partial cDNA clones were isolated that define a novel human mucin gene. These include two partial cDNA clones, SIB 124 and SIB 139, that contain 51 nucleotide tandem repeats which encode a seventeen amino acid repetitive peptide with a consensus sequence of HSTPSFTSSITTTETTS. SIB 139 hybridized to messages produced by small intestine, colon, colonic tumors and also by high mucin variant LS174T colon cancer cells. The gene from which cDNAs SIB 124 and SIB 139 are derived (proposed name MUC 3) maps to chromosome 7, distinct from other known human mucin genes.     

Control of cell type in yeast by the mating type locus: The α1-α2 hypothesis

We have extended the genetic analysis of four mutants carrying defective MATα alleles in order to determine how the mating type locus controls yeast cell types: a, a, and $\text{a}\text{α}$. First, we have mapped the defect in the mutant VC73 to the mating type locus by diploid and tetraploid segregation analysis. Second, we have determined that the mutations in these strains define two complementation groups, MATα1 and MATα2. The MATα1 gene is proposed to be a positive regulator of α mating functions. The MATα2 gene product is proposed to have two roles, as a negative regulator of a-specific mating functions and as a regulator of $\text{a}\text{α}$ cell functions (required for sporulation, for inhibition of mating and other processes). This view of MATα leads to the prediction that matα1^?matα2^? mutants should have the mating ability of an a cell and that matα1^?matα2^?/MATα strains should mate as α and be unable to sporulate. Such double mutants have been constructed and behave as predicted. We therefore propose that a-specific mating functions in MATa cells are constitutively expressed due to the absence of the MATα2 gene product and that α-specific mating functions are not expressed due to the absence of the MATα1 gene product.     

Distribution and effects of 2,4,5-trichlorophenoxyacetic acid in cells of Bacillus megaterium.

Cell death in a resting population of an asporogenous Bacillus megaterium was accelerated by ambient concentrations of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) equal to or greater than 10 mug/ml or 5 mug/mg of cells (dry weight), but only after prolonged exposure. Conversely, populations of growing cells were not markedly influenced even at 100 mug/ml. Effects on cell respiration were not manifest until the ambient concentration reached 1,000 mug of 2,4,5-T/ml, or 500 mug/mg. Cells of B. megaterium did, however, accumulate 2,4,5-T passively to a level approximately twofold above the ambient concentration. Most of the accumulated compound was easily washed from the cells, but, of the firmly bound herbicide, about 0.5 mug/mg of cells (dry weight), nearly 60% by weight, was localized in the protoplast membrane. The foregoing results, obtained with a purified preparation of 2,4,5-T were also elicited by 2,4,5-T analytical standards. The extracted contaminants did not produce the results alone nor did they influence the results when present in combination with 2,4,5-T.     

Correlation of acute with chronic hypoxic pulmonary hypertension in cattle.

We investigated acute and chronic hypoxic pulmonary pressor responses in two groups of calves, one bred to be susceptible, the other resistant to high-altitude pulmonary hypertension. Twelve 5-mo-old susceptible calves residing at 1,524 m increased their mean pulmonary arterial pressure from 26 +/- 2 (SE) to 55 +/- 4 mmHg during 2 h at a simulated altitude of 4,572 m. In 10 resistant calves pressure increased from 22 +/- 1 to 37 +/- 2 mmHg. Five calves were selected from each group for further study. When 9 mo old, the 5 susceptible calves again showed a greater pressor response to acute hypoxia (27 +/- 1 to 55 +/- 4 mmHg) than did 5 resistant calves (23 +/- 1 to 41 +/- 3 mmHg). When 12 mo old, the 5 susceptible calves also developed a greater increase in pulmonary arterial pressure (21 +/- 2 to 9 +/- 4 mmHg) during 18 days at 4,572 m than did the 5 resistant calves (21 +/- 1 to 64 +/- 4 mmHg). Acute and chronic hypoxic pulmonary pressor responses were highly correlated (r = 0.91; P less than 0.001) indicating that they were probably produced through a common mechanism.     

Interconversion of Yeast Mating Types I. Direct Observations of the Action of the Homothallism (HO) Gene

The HO gene promotes interconversion between a and α mating types. As a consequence, homothallic diploid cells are formed by mating between siblings descended from a single α HO or a HO spore. In order to determine the frequency and pattern of the mating-type switch, we have used a simple technique by which the mating phenotype can be assayed without losing the cell to the mating process itself. Specifically, we have performed pedigree analysis on descendants of single homothallic spores, testing these cells for sensitivity to α-factor.

The switch from α to a and vice versa is detectable after a minimum of two cell divisions. 50% of the clones tested showed switching by the four-cell stage. Of the four cells descended from a single cell, only the oldest cell and its immediate daughter are observed to change mating type. This pattern suggests that one event in the switching process has occurred in the first cell division cycle. Restriction of the switched mating-type to two particular cells may reflect the action of the homothallism system followed by nonrandom segregation of DNA strands in mitosis.

The mating behavior of cells which have sustained a change in mating type due to the HO gene is indistinguishable from that of heterothallic strains.

     

Properties of the cyanobacterial coupling factor ATPase from Spirulina platensis. II. Activity of the purified and membrane-bound enzymes

Cyanobacterial (Spirulina platensis) photosynthetic membranes and isolated F1 ATPase were characterized with respect to ATP activity. The following results indicate that the regulation of expression of ATPase activity in Spirulina platensis is similar to that found in chloroplasts: the ATPase activity of Spirulina membranes and isolated F1 ATPase is mostly latent, a characteristic of chloroplast ATPase activity; treatments that elicit ATPase activity in higher plant chloroplast thylakoids and isolated chloroplast coupling factor (CF1) greatly stimulate the activity of Spirulina membranes and F1, and the cation specificity of chloroplast ATPase activity, e. g., light-induced membrane activity that is magnesium dependent and trypsin-activated CF1 activity that is calcium dependent, is also observed in Spirulina. Thus, an 8- to 15-fold increase in specific activity (to 13-15 mumol Pi min-1 mg chl-1) is obtained when Spirulina membranes are treated with trypsin (CaATPase) or with methanol (MgATPase): a light-induced, dithiothreitol-dependent MgATPase activity is also found in the membranes. Purified Spirulina F1 is a CaATPase when activated with trypsin (endogenous activity increases from 4 to 27-37 mumol Pi min-1 mg protein-1) or with dithiothreitol (5.6 mumol Pi min-1 mg-1), but a MgATPase when assayed with methanol (18-20 mumol Pi min-1 mg-1). The effects of varying calcium and ATP concentrations on the kinetics of trypsin-induced CaATPase activity of Spirulina F1 were examined. When the calcium concentration is varied at constant ATP concentration, the velocity plot shows a marked sigmoidicity. By varying Ca-ATP metal-nucleotide complex concentration at constant concentrations of free calcium or ATP, it is shown that the sigmoidicity is due to the effect of free ATP, which changes the Hill constant to 1.6 from 1.0 observed when the free calcium concentration is kept constant at 5 mM. Therefore not only is ATP an inhibitor but it is also an allosteric effector of Spirulina F1 ATPase activity. At 5 mM free calcium, the Km for teh Ca-ATP metal-nucleotide complex is 0.42 mM.