Two chemotaxis-defective mutants of Pseudomonas aeruginosa, designated PC1 and PC2, were selected by the swarm plate method after N-methyl-N-nitro-N-nitrosoguanidine mutagenesis. These mutants were fully motile but incapable of swarming, suggesting that they had a defect in the intracellular signalling pathway. Computerassisted capillary assays confirmed that they failed to show behavioral responses to chemical stimuli, including peptone, methyl thiocyanate, and phosphate. Two chemotaxis genes were cloned by phenotypic complementation of PC1 and PC2. From nucleotide sequence analysis, one gene was found to encode a putative polypeptide that was homologous to the enteric CheZ protein, while the other gene was cheY, which had been previously reported (M. N. Starnbach and S. Lory, Mol. Microbiol. 6:459-469, 1992). Deletion and complementation analysis showed that PC1 was a cheY mutant, whereas PC2 had a double mutation in the cheY and cheZ genes. A chromosomal cheZ mutant, constructed by inserting a kanamycin resistance gene cassette into the wild-type gene, changed its swimming direction much more frequently than did wild-type strain PAO1. In contrast, cheY mutants were found to rarely reverse their swimming directions.Chemotaxis is the movement of an organism toward chemical attractants and away from chemical repellents (1). Pseudomonas aeruginosa is attracted to various amino acids (6) and is less strongly responsive to sugars and organic acids (15, 16). The taxis toward several amino acids is subject to control by nitrogen availability in a manner similar to the control of various enzymes of nitrogen metabolism (6) and is mediated by methylation and demethylation of methyl-accepting proteins analogous to those of the enteric bacteria (5). The strengths of the chemotactic responses to glucose and to citrate are also dependent on prior growth of the bacterial cells on those carbon sources (16). The glucose-binding protein has been identified as the glucose chemoreceptor in this organism (28). However, virtually nothing is known about the other chemoreceptors of P. aeruginosa. Our previous work demonstrated that P. aeruginosa is attracted to P i (10). This chemotactic response is induced by P i limitation. The P i -starved cells are also attracted to arsenate (11). Since P i competitively inhibits the response to arsenate, both P i and arsenate are likely to be detected by the same chemoreceptor. Genetic evidence showed that P i taxis in P. aeruginosa is not regulated by the phoB and phoR gene products but requires the phoU gene (12). P. aeruginosa is also repelled by thiocyanic and isothiocyanic esters, including allyl isothiocyanate, ethyl thiocyanate, methyl isothiocyanate, and methyl thiocyanate (19).The molecular mechanisms that underlie bacterial chemotaxis have been studied intensively with the enteric bacteria Escherichia coli (20) and Salmonella typhimurium (30) and to a lesser extent with the gram-positive bacterium Bacillus subtilis (4). However, little is known about the chemotaxis genes in the bacteri...

Lingual antimicrobial peptide (LAP) belongs to the beta-defensin family in cattle and is found in bovine milk. However, it is unclear whether LAP is involved in the early immune response to mammary infection. The aim of the study was to investigate the changes of LAP concentration in milk after intramammary challenge with lipopolysaccharide (LPS), the gram-negative bacteria cell membrane component, in dairy cows. Milk was collected before and after LPS or phosphate-buffered saline (control) challenge every hour for 12 h on d 0 and twice daily from d 1 to 7. Somatic cell count (SCC), LAP concentration, and lactoperoxidase (LPO) activity in the milk were measured. Somatic cell count started to increase at 2 h postchallenge and remained high until d 5 (694 +/- 187 x 10(3 )to >1,000 +/- 0 x 10(3) cells/mL at d 0; >1,000 +/- 0 x 10(3) cells/mL at d 1 to 3; 684 +/- 194 x 10(3 )to 829 +/- 108 x 10(3 )cells/mL at d 4; 527 +/- 197 x 10(3 )to 656 +/- 145 x 10(3 )cells/mL at d 5). Somatic cell count increased in the control cows, although the levels were lower compared with those in the LPS challenge group. The LAP concentration in milk increased significantly at 2 h post-LPS-challenge and was maintained at high levels until d 2 (8.6 +/- 0.6 to 17.5 +/- 2.3 nM). In the control cow infused with phosphate-buffered saline, there was no increase of LAP concentration in milk (5.1 +/- 0.6 to 7.2 +/- 0.8 nM). Increase of LPO activity in the milk was observed at 6 h after LPS challenge and continued until d 3 (4.7 +/- 0.3 to 9.4 +/- 1.1 U). No increase of LPO activity was observed in the milk of control cows. The increase and subsequent decrease in LAP concentration after LPS challenge occurred earlier than those of LPO activity. In multiparous cows with LPS infusion, there was a significantly negative relationship between the days leading to the basal levels in LAP concentration and LPO activity (r = -0.75). These results suggest that LPS induces secretion of LAP into milk within hours and that LPO may have a synergistic antimicrobial function with LAP in mammary glands of dairy cows.

The lingual antimicrobial peptide (LAP) belongs to the beta-defensin family in cattle and is localized in epithelial cells of alveoli in mammary glands. The aim was to investigate whether LAP is secreted into milk and whether the secreted LAP has antimicrobial activity. Decaseinated bovine skim milk was applied to sample extraction cartridges, and the eluate was used for competitive enzyme immunoassay and Western blotting to test for the presence of LAP in milk. After tricine-SDS PAGE, the gel was stained using the periodic acid-Schiff reaction to examine the possibility of glycosylation of LAP. The eluate obtained from the sample extraction cartridges was subjected to a LAP antibody-coupled affinity column, after which the antimicrobial activity of its eluate against Escherichia coli was investigated with radial diffusion plate assay and colony-forming unit enumeration following the culture of bacteria with the sample. The immunoreactive LAP was detected in the eluate by competitive enzyme immunoassay (optical density = 0.437 +/- 0.012 vs. 0.468 +/- 0.016). In the Western blotting analysis, immunoreactive bands were seen around 8, 14, and 17 kDa. The bands at 14 and 17 kDa, but not 8 kDa, were periodic acid-Schiff reaction-positive. The eluate of LAP antibody-coupled affinity column had antimicrobial activity against E. coli (cfu/control = 0.17 +/- 0.18). These results suggest that bovine milk contains functional LAP-like substances that exert antimicrobial activity.

The aim of this study was to develop an antibody to gallinacin--which is one of the antimicrobial peptides in chickens. The antibody was raised in rabbit using a synthetic peptide of gallinacin--(Gal--), and purified through an a$nity column. Specificity of antibody was examined by competitive ELISA using Gal---HRP and synthetic Gal--, or the tissue peptides isolated from the uropygial gland and the uterus. Immunostaining was performed on sections of the trachea, uterus, vagina, cloacal gland and uropygial gland. In the competitive ELISA, co-incubation of Gal---HRP with Gal--and tissue peptides extracted from uropygialis and uterus caused a clear decline of optical density (A./*) value in a dose dependent manner. The epithelial cells in the trachea, uterus, vagina, cloacal gland and uropygial gland stained positive using the prepared gallinacin--antibody. Sections incubated with antibody absorbed with Gal--(control staining) resulted in negative staining. These results suggest that the antibody to gallinacin--prepared in the current study is useful for immunocytochemical identification of gallinacin--in chickens. The current immunocytochemical results suggest the presence of gallinacin--in the epithelial cells of trachea, oviduct, cloacal gland and uropygialis.