Novel Method for Detection of Butanolides in Streptomyces coelicolor Culture Broth, Using a His-Tagged Receptor (ScbR) and Mass Spectrometry

γ-Butyrolactone derivative molecules in Streptomyces play a crucial role in cell density control, secondary metabolism, and cell differentiation. As their synthesis level in the cell is very low compared to those of similar N-acyl homoserine lactone molecules from gram-negative bacteria, it is very hard to analyze them even with several hundredfold concentration of the culture broth. We have developed a very quick and easy detection method using an affinity capture technique with His-tagged receptor proteins and electrospray tandem mass spectrometry. Using Streptomyces coelicolor as a model system, SCB1 was detected from only 100 ml of the culture broth after solvent extraction. This method can be further applied to detection and quantitative analysis of butanolides and inhibitor screening of the receptor molecules.     

Identification and characterization of a porcine parvovirus nonstructural polypeptide.

Sera from porcine parvovirus (PPV)-infected swine fetuses immunoprecipitated and 84- to 86-kilodalton polypeptide in addition to the A and B virion structural proteins. This polypeptide, designated NS-1, was present in PPV-infected cell lysates but not in purified virions. Partial proteolysis mapping revealed that NS-1 was not related to the A and B viral structural proteins. All three proteins in infected cells were phosphorylated at serine residues, and NS-1 also contained phosphothreonine. From pulse-labeling experiments with either 32Pi or [35S]methionine, NS-1 was found to first appear 5 to 7 h postinfection, whereas the viral structural polypeptides were first synthesized 9 to 11 h postinfection. Pulse-chase experiments revealed that NS-1 initially appeared as an 84-kilodalton protein and was subsequently structurally modified to forms of slower electrophoretic mobilities. The time of appearance of NS-1 after virus infection coincided with the initiation of viral DNA synthesis, suggesting that this polypeptide (and the modified forms thereof) may be involved in PPV replication.     

KBSH parvovirus: comparison with porcine parvovirus.

We compared the molecular, antigenic, and pathogenic properties of KBSH parvovirus to those of porcine parvovirus (PPV) isolate NADL-8. KBSH, propagated in swine testes cells in culture, possessed two major capsid polypeptides of 83 and 64 kilodaltons that were similar in size to those of PPV. KBSH-infected cells also contained an 86-kilodalton nonstructural polypeptide that was identical in size to the PPV nonstructural polypeptide (NS-1). The KBSH polypeptides were structurally similar but not identical to the corresponding PPV polypeptides, as revealed by partial proteolysis mapping. Viral replicative-form DNA from KBSH-infected cells was similar in size to PPV replicative-form DNA and exhibited similar but not identical restriction endonuclease cleavage patterns to that of PPV replicative-form DNA. Antigenically, the two viruses were also very closely related. By using heterologous and homologous antisera, the two viruses were indistinguishable in hemagglutination inhibition and immunoprecipitation assays. However, pathogenically these viruses were dramatically different. NADL-8 caused fetal death when injected into swine fetuses in utero and viremia and high persisting antibody titers when administered orally to weaning-age swine. KBSH-inoculated fetuses were normal in appearance, and pigs orally exposed to KBSH failed to establish viremia and demonstrated only transient antibody titers. Thus, KBSH appears to be a PPV that is very closely related to a highly pathogenic PPV isolate, yet is itself nonpathogenic in swine. This reduced pathogenic potential of KBSH may be attributable to its poor ability to replicate in swine.     

Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence

Natural selection, in the form of balancing selection or selective sweeps, can result in a decoupling of the amounts of molecular polymorphism and divergence. Thus natural selection can cause some areas of DNA sequence to have greater silent polymorphism, relative to divergence between species, than other areas. It would be useful to have a statistical test for heterogeneity in the polymorphism to divergence ratio across a region of DNA sequence, one that could identify heterogeneity greater than that expected from the neutral processes of mutation, drift, and recombination. The only currently available test requires that a region be arbitrarily divided into sections that are compared with each other, and the subjectivity of this division could be problematic. Here a test is proposed in which runs of polymorphic and fixed sites are counted, where a "run" is a set of one or more sites of one type preceded and followed by the other type. The number of runs is smaller than otherwise expected if polymorphisms are clumped together. By simulating neutral evolution and comparing the observed number of runs to the simulations, a statistical test is possible which does not require any a priori decisions about subdivision.      

An enzyme-linked immunosorbent assay (ELISA) for the detection of antisperm antibodies in horse serum

An enzyme-linked immunosorbent assay (ELISA) was developed and evaluated to detect equine antisperm antibodies (ASA) in horse serum. Six maiden mares between 12 and 18 mo of age were immunized with stallion sperm cells (SC group, N=2), seminal plasma (SP group, N=2), or phosphate-buffered saline (PBS) as a control (C group, N=2). Horses received a second injection of the same antigen 2 wk after the first. Blood was collected weekly for 10 wk after initial immunization and again at Week 15. Serum ASA levels (IgG and IgA) were measured by ELISA using two assay systems, one containing stallion SC as the plate antigen and another containing SP.

In horses immunized with SC, peak IgG levels were detected by ELISA during Wk 2 and 3 after first injection using either plate antigen. The antibody levels persisted through Week 5 and then slowly declined until Week 15. Horses immunized with SP had IgG levels that did not differ from control horses using either ELISA plate antigen. The only significant elevation in serum IgA ASA occured during Week 5 after initial immunization and only in mares immunized with SC as detected by ELISA using SC as the plate antigen. Attachment of ASA to stallion spermatozoa was confirmed by an indirect immunofluorescence assay.