Association of a 38 kDa bovine serum protein with the outer membrane of Bordetella pertussis

A series of isogenic mutants lacking either the O1 (O-:K66) or K66 (O1:K-) antigens or both (O-:K-), some of which had additional defects in their LPS core polysaccharide was used to examine the interaction between polymorphonuclear leucocytes (PMNLs) and K. pneumoniae serotype O1:K66. In the absence of serum complement, only a O-:K- strain with a deep rough LPS chemotype elicited a PMNL-dependent chemiluminescent (CL) response. However, following opsonization of the non-capsulated strains by complement, the largest CL response was to the O1:K- mutant. This mutant also activated and bound more complement C3 than any of the other encapsulated or non-capsulated strains examined. Despite the surface exposure of smooth and rough LPS in the encapsulated parent and mutant strains, the K66 antigen reduced the binding of C3 and prevented PMNL activation. Both anti-LPS and anti-K66 antibodies, however, stimulated a PMNL-dependent CL response to the K66 bearing strains.     

Growth characteristics and expression of iron-regulated outer-membrane proteins of chemostat-grown biofilm cells of Pseudomonas aeruginosa.

An in vitro chemostat system was used to study the growth and the expression of iron-regulated outer-membrane proteins (IROMPs) by biofilm cells of Pseudomonas aeruginosa cultivated under conditions of iron limitation. The population of the planktonic cells decreased when the dilution rate was increased. At a dilution rate of 0.05 h-1, the populations of planktonic cells of both mucoid and nonmucoid P. aeruginosa were 3 x 10(9) cells/mL. This value dropped to 5 x 10(6) cells/mL when the dilution rate was increased to 1.0 h-1. The reverse was observed for the biofilm cells. The number of biofilm cells colonising the silicone tubing increased when the dilution rate was increased. The number of biofilm cells of the mucoid strain at steady state was 2 x 10(8) cells/cm (length) when the dilution rate was fixed at 0.05 h-1. The figure increased to 8 x 10(9) cells/cm when the dilution rate was increased to 1.0 h-1. The population of biofilm cells of the nonmucoid strain was 9 x 10(7) cells/cm (length) when the dilution rate was 0.05 h-1. It increased to 2 x 10(9) cells/cm when the dilution rate was set at 1.0 h-1. The expression of IROMPs was induced in the biofilm cells of both mucoid and nonmucoid strains when the dilution rates were 0.05 and 0.2 h-1. IROMPs were reduced but still detectable at the dilution rate of 0.5 h-1. However, the expression of IROMPs was repressed when the dilution rate was increased to 1.0 h-1. The data suggest that the biofilm cells of P. aeruginosa switch on the expression of IROMPs to assist iron acquisition when the dilution rate used for the chemostat run is below 0.5 h-1. The high affinity iron uptake system is not required by the biofilm cells when the dilution rate is increased because the trace amount of iron present in the chemostat is sufficient for the growth of adherent biofilm cells.     

Kinetics of uranous iron and ferrous iron oxidation by thiobacillus ferrooxidans

Archives of Microbiology -     

Carbon determination in human teeth by activation with He-3 ions

A nuclear analytical method, involving activation with³He ions, was developed to determine carbon content in human teeth with well-documented histories. The tooth samples were irradiated with 2.7-MeV³He particles at 50 nA intensity, and the activity of¹⁴O induced through the reaction¹²C(³He, n)¹⁴O, determined by counting the 2.31-MeV gammas. Different dental hard tissues were studied separately. A solid piece of silver steel, the carbon content of which was accurately determined by chemical means, was used as the standard. The carbon content in different teeth varied from 4–7%. The overall experimental accuracy was better than 4.5%.

     

中国鸡皮衣属和泡鳞衣属地衣2个新记录种

报道了采自中国西北部新疆博格达山区哈熊沟森林公园的鸡皮衣属和泡鳞衣属地衣的2个中国新记录种,即南方鸡皮衣(Pertusaria australis Vian)和北极泡鳞衣(Toninia arctica Timdal),并描述了二者的形态学、解剖学以及化学成分特征,提供了其形态特征和内部解剖结构照片.标本保存于新疆大学...     

Microbiological Analysis of Tube-Well Water in a Rural Area of Bangladesh

Five tube-wells in Matlab, Bangladesh, were selected for analysis of selected biophysicochemical parameters. The results showed that all tube-well water samples contained zooplankton and bacteria. Results for some of the parameters were outside the accepted limits recommended by the World Health Organization for drinking water. It is concluded that water from tube-wells should be treated if used as drinking water.     

Sequencing and Expression of a β-Mannanase Gene from the Extreme Thermophile Dictyoglomus thermophilum Rt46B.1, and Characteristics of the Recombinant Enzyme

A β-mannanase gene (manA) was isolated from the extremely thermophilic bacterium Dictyoglomus thermophilum Rt46B.1. ManA is a single-domain enzyme related to one group of β-mannanases (glycosyl hydrolase family 26). The manA gene was expressed in the heat-inducible vector pJLA602 and the expression product, ManA, purified to homogeneity. The recombinant ManA is a monomeric enzyme with a molecular mass of 40 kDa and an optimal temperature and pH for activity of 80°C and 5.0. In the absence of substrate, the enzyme showed no loss of activity at 80°C over 16 h, while at 90°C the enzyme had a half-life of 5.4 min. Hydrolysis of the galactomannan locust bean gum (LBG) by purified ManA released mainly mannose, mannobiose, and mannotriose, confirming that ManA is an endo-acting β-mannanase. Sequence comparisons with related β-mannanases has allowed the design of consensus PCR primers for the identification and isolation of related genes. Received: 7 June 1999 / Accepted: 6 July 1999     

Nematicidal Activity of Some Phenolics on Root Knot, Growth and Yield of Capsicum frutescens cv. California Wonder

Abstract Free living nematode Caenorhabditis elegans was used as a test system for screening anthelmintic phenolics. The most effective concentrations (100, 500 and 1000 μg ml⁻¹) were used against root knot nematode Meloidogyne incognita. Effect of these phenolics was determined on growth and development of host plant Capsicum frutescens cv. California Wonder, Second stage juveniles of M. incognita were hatched from egg masses collected from roots of host plant and subjected to similar phenol concentrations for 48 h. Mortality of M. incognita was recorded on the basis of parameters used for test organism bioassay. Both healthy and inoculated plants of C. frutescens cv. California Wonder were treated withsolutions of salicylic acid (SA) and p-betahydroxy benzoic acid (BA) so that each pot received 100, 500 and 1000 mg phenol. Control plants were supplied with distilled water, Plants were uprooted 21 days after inoculation and roots were gall indexed. Some plants were left in the pots for further growth and development. Surface sterilised seedlings of host plant were raised and inoculated with second stage Juveniles of M. incognita. Thereafter observations were recorded on the vegetative and reproductive parameters of the plants. Drench application of SA and BA were found quite effective with no apparent phytotoxic effect.