Protein evolution of ANTP and PRD homeobox genes

Background  

Although homeobox genes have been the subject of many studies, little is known about the main amino acid changes that occurred early in the evolution of genes belonging to different classes.     

HPLC based method for the measurement of the reduction of aflatoxin B<Subscript>1</Subscript> by bacterial cultures isolated from different African foods

The consumption of fermented foods contaminated with aflatoxin B₁ is linked to aflatoxicosis. Aflatoxicosis is a serious problem in developing countries with environmental conditions appropriate for the biosynthesis of AFB₁ byAspergillus flavus andAspergillus parasiticus. In Africa, especially in Ghana and Nigeria, there is a very high risk of liver cancer which is caused by the consumption of AFB₁-intoxicated, traditionally fermented maize and sorghum products. It is suggested that one way to diminish this health risk might be the reduction of the AFB₁ concentration in foods by bacteria. Especially bacteria used for food fermentation processes are of great importance, with a special emphasis on lactic acid bacteria which are involved in traditionally fermented African foods based on maize and sorghum.Most publications dealing with aflatoxin degradation by microorganisms describe a phosphate buffer test system for the performance of degradation experiments. In contrast to that, a test system based on physiological active bacterial and yeast cells has been developed, to assess food fermentation organisms for their ability to reduce the AFB₁ concentration in vitro. The aflatoxin B₁ concentration in test samples was quatitatively determined by HPLC.The assessment of lactic acid bacteria originating from different German and other European culture collections only showed a very slight reduction of the AFB₁ concentration from 3% to 12%. Screening experiments in which other bacterial genera and lactic acid bacteria, isolated from different African foods have been assessed, in most cases showed the same results. However, some bacterial strains, e.g. strains of the genusBacillus derived from European culture collections and strains of the genusLactobacillus isolated from African foods, caused a release of AFB₁ which was chemically bound before to components of the test medium and which therefore could not be extracted with chloroform.A process quite similar to that may happen during food fermentations. Different experiments showed that e.g. cellulose can bind AFB₁ very effectively. Cellulose and different other food components are well known to absorb AFB₁. During fermentation the cellulose and other AFB₁-absorbing components may be degraded and the AFB₁ will be released again.The only bacterial strain known as yet which is able to reduce the AFB₁ concentration in vitro and in different food comodities isNocardia corynebacteroides (formerFlavobacterium aurantiacum). Nevertheless the mechanism of this AFB₁ reduction is actually not well understood, it still has to be investigated. In the meantime several other bacterial strains, presumably from the taxonomic group of theActinomycetes could be proved to be effective reducers of the AFB₁ concentration in our in vitro test system. Because as yet no food relevant microorganism could be found, which is able to degrade AFB₁, these new strains in general offer the possibility for a genetic modification of food relevant microorganisms. This seems to be the way to come to starter cultures which are able to degrade AFB₁ during food fermentations.     

Translocation of Sickle Cell Erythrocyte MicroRNAs into Plasmodium falciparum Inhibits Parasite Translation and Contributes to Malaria Resistance

Erythrocytes carrying a variant hemoglobin allele (HbS), which causes sickle cell disease and resists infection by the malaria parasite Plasmodium falciparum. The molecular basis of this resistance, which has long been recognized as multifactorial, remains incompletely understood. Here we show that the dysregulated microRNA (miRNA) composition, of either heterozygous HbAS or homozygous HbSS erythrocytes, contributes to resistance against P.?falciparum. During the intraerythrocytic life cycle of P.?falciparum, a subset of erythrocyte miRNAs translocate into the parasite. Two miRNAs, miR-451 and let-7i, were highly enriched in HbAS and HbSS erythrocytes, and these miRNAs, along with miR-223, negatively regulated parasite growth. Surprisingly, we found that miR-451 and let-7i integrated into essential parasite messenger RNAs and, via impaired ribosomal loading, resulted in translational inhibition. Hence, sickle cell erythrocytes exhibit cell-intrinsic resistance to malaria in part through an?atypical miRNA activity, which may represent?a unique host defense strategy against complex eukaryotic pathogens.     

Flagella Overexpression Attenuates Salmonella Pathogenesis

Flagella are cell surface appendages involved in a number of bacterial behaviors, such as motility, biofilm formation, and chemotaxis. Despite these important functions, flagella can pose a liability to a bacterium when serving as potent immunogens resulting in the stimulation of the innate and adaptive immune systems. Previous work showing appendage overexpression, referred to as attenuating gene expression (AGE), was found to enfeeble wild-type Salmonella. Thus, this approach was adapted to discern whether flagella overexpression could induce similar attenuation. To test its feasibility, flagellar filament subunit FliC and flagellar regulon master regulator FlhDC were overexpressed in Salmonella enterica serovar Typhimurium wild-type strain H71. The results show that the expression of either FliC or FlhDC alone, and co-expression of the two, significantly attenuates Salmonella. The flagellated bacilli were unable to replicate within macrophages and thus were not lethal to mice. In-depth investigation suggests that flagellum-mediated AGE was due to the disruptive effects of flagella on the bacterial membrane, resulting in heightened susceptibilities to hydrogen peroxide and bile. Furthermore, flagellum-attenuated Salmonella elicited elevated immune responses to Salmonella presumably via FliC’s adjuvant effect and conferred robust protection against wild-type Salmonella challenge.     

The rate of synonymous substitution in enterobacterial genes is inversely related to codon usage bias

Genes sequences from Escherichia coli, Salmonella typhimurium, and other members of the Enterobacteriaceae show a negative correlation between the degree of synonymous-codon usage bias and the rate of nucleotide substitution at synonymous sites. In particular, very highly expressed genes have very biased codon usage and accumulate synonymous substitutions very slowly. In contrast, there is little correlation between the degree of codon bias and the rate of protein evolution. It is concluded that both the rate of synonymous substitution and the degree of codon usage bias largely reflect the intensity of selection at the translational level. Because of the high variability among genes in rates of synonymous substitution, separate molecular clocks of synonymous substitution might be required for different genes.      

Diffusion permeability and ultrafiltration-reflection-coefficients of Narand Cl- in the near-term placenta of the sheep

Experiments were performed on unanaesthetized ewes in the last third of pregnancy. Fetuses and ewes had indwelling vascular catheters. In some of the experiments fetal urine was drained to the exterior by means of an indwelling vesicular catheter. Placental diffusion permeabilities were measured with 22Na+ and 36Cl- injected into eight fetuses. Volumes of distribution of Na+ and Cl- in the conceptus were Na+: 548 +/- 24, Cl-: 760 +/- 51 (ml/kg fetal wt +/- SEM). Diffusion permeabilities were Na+: 5.2 X 10(-3) +/- 0.3 X 10(-3), Cl-: 9.8 X 10(-3) +/- 0.9 X 10(-3) (ml.s-1.kg-1 +/- SEM). Ultrafiltration-reflection-coefficients of Na+ and Cl- in the placental exchange barrier were measured 17 times in seven fetuses with vesicular catheters. The transplacental e.m.f. was estimated from these results, on the assumption that the individual reflection-coefficients of Na+ should correlate with those of Cl-. The best estimate was -1.0 mV (fetus negative), and the best estimates of the placental reflection-coefficients were Na+: 0.83 and Cl-: 0.79. There was a reliable negative correlation (P < 0.01) between the calculated reflection-coefficients and the osmolality of the urine secreted by the fetus. This suggested that the concentration of vasopressin in fetal plasma affects the membrane characteristics of the placenta. The mean total osmotic force across the placental barrier of the sheep in these experiments was calculated to be 260 Pa (2 mmHg).