Antimycin A-producing nonphytopathogenic Streptomyces turgidiscabies from potato

Aim:  To detect if substances with mammalian cell toxicity are produced by Streptomyces turgidiscabies and Streptomyces scabiei isolated from potato scab lesions. Methods and Results:  In vitro cultures of phytopathogenic and nonphytopathogenic strains of S. scabiei and S. turgidiscabies, isolated from scab lesions of potato tubers originating from nine different cultivars from Finland and Sweden, were tested for toxicity using the rapid spermatozoan motility inhibition assay, previously shown useful in the detection of many different Streptomyces toxins and antimicrobial compounds. Purified toxins were used as reference. Three nonphytopathogenic strains of S. turgidiscabies were found to produce antimycin A when cultured on solid medium. Conclusions:  Boar sperm-motility-inhibiting substances are produced by strains of S. turgidiscabies and S. scabiei. The most powerful inhibitory substance, produced by three nonphytopathogenic S. turgidiscabies strains, was identified as antimycin A. The phytotoxic compounds thaxtomin A and concanamycin A did not inhibit sperm motility even at high doses. Significance and Impact of the Study:  The presence of antimycin A-producing Streptomyces strains, nonpathogenic to potato, was unexpected but important, considering the high mammalian toxicity of this cytochrome bc-blocking antibiotic.     

Group-specific quantification of methanotrophs in landfill gas-purged laboratory biofilters by tyramide signal amplification-fluorescence in situ hybridization

The aim of this study was to quantitatively analyse methanotrophs in two laboratory landfill biofilters at different biofilter depths and at temperatures which mimicked the boreal climatic conditions. Both biofilters were dominated by type I methanotrophs. The biofilter depth profiles showed that type I methanotrophs occurred in the upper layer, where relatively high O(2) and low CH(4) concentrations were present, whereas type II methanotrophs were mostly distributed in the zone with high CH(4) and low O(2) concentrations. The number of type I methanotrophic cells declined when the temperature was raised from 15 degrees C to 23 degrees C, but increased when lowered to 5 degrees C. A slight decrease in type II methanotrophs was also observed when the temperature was raised from 15 degrees C to 23 degrees C, whereas cell numbers remained constant when lowered to 5 degrees C. The results indicated that low temperature conditions favored both type I and type II methanotrophs in the biofilters.     

Relationship between decomposition of cellulose strips and chemical properties of humus layer in natural boreal forests

The relationships between the decomposition of cellulose strips buried completely within the humus layer (Of + Oh) for two 1-year periods and humus layer properties were studied at forested sites with minimal anthropogenic influence. The 18 study sites are clustered in four catchments located between 61° and 69° N in Finland. The stands were composed of varying proportions of Scots pine, Norway spruce and deciduous species. Of the 23 humus layer properties studied, significant correlations were found between decomposition and soil pH, effective cation exchange capacity, base saturation, C/N ratio, the concentrations of P, Mn, Pb, Zn and Cu. The relationships, however, were inconsistent except for heavy metal concentrations which were positive in all cases. Decomposition was more strongly and consistently correlated to tree stand characteristics (mean height and stem volume) than to the humus layer properties. Both the decomposition of cellulose strips and the concentrations of heavy metals were intercorrelated with climate and the stand characteristics. Partial correlation analysis revealed that the relationships between decomposition and humus layer heavy metal concentrations were more strongly affected by the tree stand characteristics than by climate. After the statistical elimination of the effects of stand characteristics, no significant positive correlations between decomposition and humus layer heavy metal concentrations remained and, in some cases for total and extractable Zn, the correlations became significant and negative. Results from litterfall chemistry (nutrients and heavy metals) also underlined that any specific effects of humus layer heavy metal concentrations on decomposition may be masked if the effects of stand characteristics are not accounted for. We conclude that the relationships between decomposition and soil chemical properties can not be elucidated without considering stand structure and composition of the forest stand.     

Degradation of paper mill water components in laboratory tests with pure cultures of bacteria

The degradation of dissolved and colloidal substances from thermomechanical pulp (TMP) by bacteria isolated from a paper mill was studied in a laboratory slide culture system.Burkholderia cepacia strains hydrolysed triglycerides to free fatty acids, and the liberated unsaturated fatty acids were then degraded to some extent. Saturated fatty acids were not notably degraded. However, the branched anteiso-heptadecanoic fatty acid was degraded almost like the unsaturated fatty acids. About 30% of the steryl esters were degraded during 11 days, increasing the concentrations of free sterols. Approximately 25% of the dehydroabietic, and 45% of the abietic and isopimaric resin acids were degraded during 11 days. The degree of unsaturation seemed to be of greater importance for the degradation of fatty acids than the molar mass. No degradation of dissolved hemicelluloses could be observed with any of the nine bacterial strains studied. Burkholderia cepacia strains and one Bacillus coagulans strain degraded monomeric fructose and glucose in winter TMP water, but in summer TMP water, with much lower sugar concentrations, also otherBacillus strains degraded monomeric sugars.     

TCR affinity promotes CD8+ T cell expansion by regulating survival

Ligation with high affinity ligands are known to induce T lymphocytes to become fully activated effector cells while ligation with low affinity ligands (or partial agonists) may result in a delayed or incomplete response. We have examined the quantitative features of CD8(+) T cell proliferation induced by peptides of different TCR affinities at a range of concentrations in the mouse OT-I model. Both the frequency of cells responding and the average time taken for cells to reach their first division are affected by peptide concentration and affinity. Consecutive division times, however, remained largely unaffected by these variables. Importantly, we identified affinity to be the sole regulator of cell death in subsequent division. These results suggest a mechanism whereby TCR affinity detection can modulate the subsequent rate of T cell growth and ensure the dominance of higher affinity clones over time.     

Measuring lymphocyte proliferation, survival and differentiation using CFSE time-series data

Cellular proliferation is an essential feature of the adaptive immune response. The introduction of the division tracking dye carboxyfluorescein diacetate succinimidyl ester (CFSE) has made it possible to monitor the number of cell divisions during proliferation and to examine the relationship between proliferation and differentiation. Although qualitative examination of CFSE data may be useful, substantially more information about division and death rates can be extracted from quantitative CFSE time-series experiments. Quantitative methods can reveal in detail how lymphocyte proliferation and survival are regulated and altered by signals such as those received from co-stimulatory molecules, drugs and genetic polymorphisms. In this protocol, we present a detailed method for examining time-series data using graphical and computer-based procedures available to all experimenters.     

Distinct patterns of genetic variation in Pristionchus pacificus and Caenorhabditis elegans, two partially selfing nematodes with cosmopolitan distribution

Hermaphroditism has evolved several times independently in nematodes. The model organism Caenorhabditis elegans and Pristionchus pacificus are self-fertile hermaphrodites with rare facultative males. Both species are members of different families: C. elegans belongs to the Rhabditidae and P. pacificus to the Diplogastridae. Also, both species differ in their ecology: C. elegans is a soil-dwelling nematode that is often found in compost heaps. In contrast, field studies in Europe and North America indicate that Pristionchus nematodes are closely associated with scarab beetles. In C. elegans, several recent studies have found low genetic diversity and rare out-crossing events. Little is known about diversity levels and population structure in free-living hermaphroditic nematodes outside the genus Caenorhabditis. Taking a comparative approach, we analyse patterns of molecular diversity and linkage disequilibrium in 18 strains of P. pacificus from eight countries and four continents. Mitochondrial sequence data of P. pacificus isolates reveal a substantially higher genetic diversity on a global scale when compared to C. elegans. A mitochondrial-derived hermaphrodite phylogeny shows little geographic structuring, indicating several worldwide dispersal events. Amplified fragment length polymorphism and single strand conformation polymorphism analyses demonstrate a high degree of genome-wide linkage disequilibrium, which also extends to the mitochondrial genome. Together, these findings indicate distinct patterns of genetic variation of the two species. The low level of genetic diversity observed in C. elegans might reflect a recent human-associated dispersal, whereas the P. pacificus diversity might reflect a long-lasting and ongoing insect association. Thus, despite similar lifestyle characteristics in the laboratory, the reproductive mode of hermaphroditism with rare facultative males can result in distinct genetic variability patterns in different ecological settings.     

Impact of biological factors on the ennoblement of stainless steel in Baltic seawater

Open circuit potentials of stainless steels increased when immersed in the Baltic Sea. The ennoblement potential was +200 mV_sce in 40 to 50 days when sea water temperature was below 52°C and +300–400 mV_sce within <40 days at around 102°C. Ennoblement occurred in a laboratory ecosystem at 232°C in 20 to 30 days, and at 262°C in <20 days, but no ennoblement occurred at A322°C within 40 days. By the time the ennoblement was complete, compact microcolonies covered 1–10% of the steel surface. Nutrient enrichment of Baltic Sea water by twofold above the natural levels increased microbial growth but attenuated open circuit potential increase of the stainless steels. Exposure of the ennobled stainless steels to similar levels of nutrients did not reverse the already developed open circuit potentials. Attenuation of the ennobling response of the stainless steels by increases of temperature and eutrophication suggests a role for microorganisms which is crucial for the electrochemical behaviour of steels in brackish Baltic Sea water. Journal of Industrial Microbiology & Biotechnology (2000) 24, 410–420. Received 02 November 1999/ Accepted in revised form 24 March 2000     

Comparison of culture, enzyme immunoassay and nucleic acid sandwich hybridization in detecting Chlamydia trachomatis in genital tract infections

Abstract Culture, enzyme immunoassay (Chlamydiazyme™) and nucleic acid sandwich hybridization were compared in detecting Chlamydia trachomatis in uncomplicated genital tract infections. Urethral and cervical specimens were collected from 100 males and 100 females attending a sexually transmitted disease clinic. Chlamydial culture was performed under optimal conditions (duplicate inoculation within the day specimen was collected, culture in vials, monoclonal antibody staining of inclusions, blind passage for negative samples). Here the sensitivity of culture exceeded that of the rapid methods. The sensitivity of a chlamydial antigen detection method (Chlamydiazyme™) was 68% in male and 86% in female specimens, when compared with culture, and the specificity was 100% and 97%, respectively. Acinetobacter calcoace9icus present in clinical specimens did not interfere with Chlamydiazyme™. The sensitivity of the nucleic acid sandwich hybridization was 53% of that of the culture, and specificity 100%. By comparing the three methods it was apparent that the rapid methods did not reveal chlamydial infections not detectable by culture. Thus, if performed carefully, culture is the most sensitive diagnostic method in acute genital infections due to C. trachomatis .