Effects of Bacteriophages on the Population Dynamics of Four Strains of Pelagic Marine Bacteria

Viral lysis of specific bacterial populations has been suggested to be an important factor for structuring marine bacterioplankton communities. In the present study, the influence of bacteriophages on the diversity and population dynamics of four marine bacterial phage-host systems was studied experimentally in continuous cultures and theoretically by a mathematical model. By use of whole genome DNA hybridization toward community DNA, we analyzed the dynamics of individual bacterial host populations in response to the addition of their specific phage in continuous cultures of mixed bacterial assemblages. In these experiments, viral lysis had only temporary effects on the dynamics and diversity of the individual bacterial host species. Following the initial lysis of sensitive host cells, growth of phage-resistant clones of the added bacteria resulted in a distribution of bacterial strains in the phage-enriched culture that was similar to that in the control culture without phages after about 50-60 h incubation. Consequently, after a time frame of 5-10 generations after lysis, it was the interspecies competition rather than viral lysis of specific bacterial strains that was the driving force in the regulation of bacterial species composition in these experiments. The clonal diversity, on the other hand, was strongly influenced by viral activity, since the clonal composition of the four species in the phage-enriched culture changed completely from phage-sensitive to phage-resistant clones. The model simulation predicted that viral lysis had a strong impact on the population dynamics, the species composition, and the clonal composition of the bacterial community over longer time scales (weeks). However, according to the model, the overall density of bacteria in the system was not affected by phages, since resistant clones complemented the fluctuations caused by viral lysis. Based on the model analysis, we therefore suggest that viral lysis can have a strong influence on the dynamics of bacterial populations in planktonic marine systems.     

Specific features of early embryogenesis in apomictic Poa pratensis L

We studied the early stages of embryo formation in apomictic Poa partensis L. It was shown that during transition to parthenogenesis, at least at the initial stages of embryogenesis, the algorithm of development of the sexual embryo is preserved. This could be due to the system of genetic control of embryogenesis, common for amphimixis and apomixis. We described asynchrony of developmental processes both within the efflorescence (asynchronous maturation of ovules) and within the ovule and even gametophyte (different timing of induction of apoarchesporic initials and oospores). This feature of pseudogamous apomicts allows them to produce simultaneously both sexual and apomictic progenies.     

Dependence of rifabutin properties and liposome entrapment on pH of the medium]

Rifabutin solubility within pH 3.0 to 11.0 was determined. Potentiometry, spectrophotometry and computation revealed ionization of three groups with pKa 3.5, 6.5 and 9.5 in the rifabutin molecule. On the basis of the pKa values of certain fragments of the rifabutin molecule computed by the ACD/pKa programme they were related to ionization of the following groups: imidazole residue nitrogen, aromatic hydoxyl and piperidin nitrogen respectively. Interaction of rifabutin with model membranes, i. e. large unilamellar vesicules was studied. At lower pH of the medium, entrapment of rifabutin to the large unilamellar vesicules increased that was evident of satisfactory correlation with the decrease in the rifabutin distribution coefficient in the system multilamellar vesicules/water under the experimental conditions.     

Lactobacilli Inactivate Chlamydia trachomatis through Lactic Acid but Not H2O2

Lactobacillus species dominate the microbiome in the lower genital tract of most reproductive-age women. Producing lactic acid and H₂O₂, lactobacilli are believed to play an important role in prevention of colonization by and growth of pathogens. However, to date, there have been no reported studies characterizing how lactobacilli interact with Chlamydia trachomatis, a leading sexually transmitted bacterium. In this report, we demonstrate inactivation of C. trachomatis infectivity by culture media conditioned by Lactobacillus crispatus, L. gasseri and L. jensenii, known to be dominating organisms in the human vaginal microbiome. Lactobacillus still cultures produced lactic acid, leading to time- and concentration-dependent killing of C. trachomatis. Neutralization of the acidic media completely reversed chlamydia killing. Addition of lactic acid into Lactobacillus-unconditioned growth medium recapitulated the chlamydiacidal activity of conditioned media. The H₂O₂ concentrations in the still cultures were found to be comparable to those reported for the cervicovaginal fluid, but insufficient to inactivate chlamydiae. Aeration of Lactobacillus cultures by shaking markedly induced H₂O₂ production, but strongly inhibited Lactobacillus growth and lactic acid production, and thus severely affected acidification, leading to significantly reduced chlamydiacidal efficiency. These observations indicate lactobacilli inactivate chlamydiae primarily through maintaining acidity in a relatively hypoxic environment in the vaginal lumen with limited H₂O₂, which is consistent with the notion that women with higher vaginal pH are more prone to sexually transmitted C. trachomatis infection. In addition to lactic acid, formic acid and acetic acid also exhibited potent chlamydiacidal activities. Taken together, our findings imply that lowering the vaginal pH through engineering of the vaginal microbiome and other means will make women less susceptible to C. trachomatis infection.     

Cervical lymph node metastases of thyroid carcinoma - an alternative of the "lateral aberrant thyroid"

The neoplastic thyroid tissue found in the laterocervical lymph nodes of euthyroid patients is associated with an intrathyroid carcinoma identified in the subsequently operated gland, asserting its metastic origin. Eighty percent of the thyroid carcinomas present cervical metastases in a variable number of lymph nodes belonging to more than one topographic group.     

A Comparison of Assays for Accurate Copy Number Measurement of the Low-Affinity Fc Gamma Receptor Genes FCGR3A and FCGR3B

The FCGR3 locus encoding the low affinity activating receptor FcγRIII, plays a vital role in immunity triggered by cellular effector and regulatory functions. Copy number of the genes FCGR3A and FCGR3B has previously been reported to affect susceptibility to several autoimmune diseases and chronic inflammatory conditions. However, such genetic association studies often yield inconsistent results; hence require assays that are robust with low error rate. We investigated the accuracy and efficiency in estimating FCGR3 CNV by comparing Sequenom MassARRAY and paralogue ratio test-restriction enzyme digest variant ratio (PRT-REDVR). In addition, since many genetic association studies of FCGR3B CNV were carried out using real-time quantitative PCR, we have also included the evaluation of that method’s performance in estimating the multi-allelic CNV of FCGR3B. The qPCR assay exhibited a considerably broader distribution of signal intensity, potentially introducing error in estimation of copy number and higher false positive rates. Both Sequenom and PRT-REDVR showed lesser systematic bias, but Sequenom skewed towards copy number normal (CN = 2). The discrepancy between Sequenom and PRT-REDVR might be attributed either to batch effects noise in individual measurements. Our study suggests that PRT-REDVR is more robust and accurate in genotyping the CNV of FCGR3, but highlights the needs of multiple independent assays for extensive validation when performing a genetic association study with multi-allelic CNVs.     

Effects of microwaves on the puffing pattern of <Emphasis Type="Italic">D. melanogaster</Emphasis>

The influence of electromagnetic field exposure on puffing pattern of salivary gland polythene chromosomes, viability and fertility of Drosophila melanogaster of the wild type Canton-S line was studied. Experimental conditions: Electromagnetic field characteristics: frequency — 36.64 GHz, power density — 0.4 W/m², exposure time −10 seconds. Electromagnetic field exposure was conducted on the egg stage. Results: in larvae developed from the exposed eggs 3 of 8 chromosomal puffs tested (71CE, 82EF, and 83E) had significantly smaller dimensions than these in control at the prepupal stage. Viability of Drosophila estimated by the number of adult flies hatched from exposed eggs decreased, while the number of dominant lethal mutations increased. Conclusion: the exposure to a low-level microwave irradiation suppressed puffing activity at ecdysone-inducible loci of Drosophila polythene chromosomes, increased frequency of dominant lethal mutations and decreased Drosophila viability but did not influence Drosophila fertility.