Interactions between rumen amylolytic and lactate-utilizing bacteria in growth on starch

The growth and metabolism of the rumen amylolytic bacteria Streptococcus bovis, Butyrivibrio fibrisolvens and Bacteroides ruminicola, growing in pure cultures and co-cultures with the rumen lactilytic bacteria Megasphaera elsdenii and Veillonella alcalescens were followed. The interaction of amylolytic bacteria with V. alcalescens represents a simple food chain. The interaction with M. elsdenii is more complex, since there is a simultaneous competition for products of the starch degradation.     

Metabolism and some characteristics of ruminal strains of Megasphaera elsdenii.

Megasphaera elsdenii belongs to the group comprising the ruminal and intestinal lactate- and sugar-fermenting species. In the present study the fermentation characteristics, metabolism of glucose and lactate, and susceptibility to antimicrobial agents of four ruminal strains were investigated. Particular attention was given to the mixed-substrate fermentation pattern and resultant fermentation acid profile. Lactate was utilized more rapidly than glucose in media with both carbon sources. Interaction of the two substrates changed the composition of fermentation end products toward more valerate and less propionate in cultures with glucose and lactate. Contrary to the indications in Bergey's Manual of Systematic Bacteriology, butyrate, not caproate, was the main end product of glucose metabolism. The strains examined were rather insensitive to many antimicrobial compounds, especially to ionophores and other antimicrobial feed additives.     

Interactions between rumen amylolytic and lactate-utilizing bacteria in growth on starch

The growth and metabolism of the rumen amylolytic bacteria Streptococcus bovis, Butyrivibrio fibrisolvens and Bacteroides ruminicola , growing in pure cultures and co-cultures with the rumen lactilytic bacteria Megasphera elsdenii and Veillonella alcalescens were followed. The interaction of amylolytic bacteria with V. alcalescens represents a simple food chain. The interaction with M. elsdenii is more complex, since there is a simultaneous competition for products of the starch degradation.     

Reciprocal allopolyploid grasses (Festuca × Lolium) display stable patterns of genome dominance

Allopolyploidization entailing the merger of two distinct genomes in a single hybrid organism, is an important process in plant evolution and a valuable tool in breeding programs. Newly established hybrids often experience massive genomic perturbations, including karyotype reshuffling and gene expression modifications. These phenomena may be asymmetric with respect to the two progenitors, with one of the parental genomes being “dominant.” Such “genome dominance” can manifest in several ways, including biased homoeolog gene expression and expression level dominance. Here we employed a k-mer–based approach to study gene expression in reciprocal Festuca pratensis Huds. × Lolium multiflorum Lam. allopolyploid grasses. Our study revealed significantly more genes where expression mimicked that of the Lolium parent compared with the Festuca parent. This genome dominance was heritable to successive generation and its direction was only slightly modified by environmental conditions and plant age. Our results suggest that Lolium genome dominance was at least partially caused by its more efficient trans-acting gene expression regulatory factors. Unraveling the mechanisms responsible for propagation of parent-specific traits in hybrid crops contributes to our understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies.     

Mechanistic Basis for Type 2 Long QT Syndrome Caused by KCNH2 Mutations that Disrupt Conserved Arginine Residues in the Voltage Sensor

KCNH2 encodes the Kv11.1 channel, which conducts the rapidly activating delayed rectifier K⁺ current (I _Kr) in the heart. KCNH2 mutations cause type 2 long QT syndrome (LQT2), which increases the risk for life-threatening ventricular arrhythmias. LQT2 mutations are predicted to prolong the cardiac action potential (AP) by reducing I _Kr during repolarization. Kv11.1 contains several conserved basic amino acids in the fourth transmembrane segment (S4) of the voltage sensor that are important for normal channel trafficking and gating. This study sought to determine the mechanism(s) by which LQT2 mutations at conserved arginine residues in S4 (R531Q, R531W or R534L) alter Kv11.1 function. Western blot analyses of HEK293 cells transiently expressing R531Q, R531W or R534L suggested that only R534L inhibited Kv11.1 trafficking. Voltage-clamping experiments showed that R531Q or R531W dramatically altered Kv11.1 current (I _Kv11.1) activation, inactivation, recovery from inactivation and deactivation. Coexpression of wild type (to mimic the patients’ genotypes) mostly corrected the changes in I _Kv11.1 activation and inactivation, but deactivation kinetics were still faster. Computational simulations using a human ventricular AP model showed that accelerating deactivation rates was sufficient to prolong the AP, but these effects were minimal compared to simply reducing I _Kr. These are the first data to demonstrate that coexpressing wild type can correct activation and inactivation dysfunction caused by mutations at a critical voltage-sensing residue in Kv11.1. We conclude that some Kv11.1 mutations might accelerate deactivation to cause LQT2 but that the ventricular AP duration is much more sensitive to mutations that decrease I _Kr. This likely explains why most LQT2 mutations are nonsense or trafficking-deficient.     

Spatial patterns of extra‐pair paternity for spotted towhees Pipilo maculatus in urban parks

The extra‐pair (EP) mating system of birds may be influenced by food resources, such that nutritionally stressed females are unable to pursue EP fertilizations (constrained female hypothesis; CFH), or that females on poor territories acquire EP fertilizations during extra‐territorial forays in search of food (mating opportunity hypothesis; MOH). Edges of urban habitat fragments are sites of apparent high food abundance for spotted towhees Pipilo maculatus, and we used distance to habitat edge in four urban parks in Portland, OR, USA (2004–2006), to test the CFH and MOH. EP paternity was independent of park identity and year; 44% of nests contained EP young and 26% of all young were EP. As predicted by the CFH, EP paternity was more common in nests of long‐tailed (presumably) high quality females. However, independently of tail length, younger females had more EP young than older females, a finding consistent with the MOH. Contrary to predictions of both hypotheses, the probability that a nest contained EP young was highest both at the habitat edge and habitat interior while the proportion of young in nests of EP origin (for nests with EP young) was highest at intermediate distances from habitat edge. We propose that high frequency of EP paternity among females in the interior occurred because, as predicted by the MOH, they ranged more widely in search of food and often encountered EP males. High probability of EP paternity near edges was likely unrelated to female quality. Instead, anthropogenic food sources may have attracted individuals to edges and increased encounters between potential EP mates. Simple opportunity seems likely to account for patterns of EP paternity in spotted towhees, suggesting that human altered environments have the potential to substantially affect EP mating behavior.     

Structural protein analysis of the polyvalent staphylococcal bacteriophage 812

Phage 812 is a polyvalent phage with a very broad host range in the genus Staphylococcus, which makes it a suitable candidate for phage therapy of staphylococcal infections. This proteomic study, combining the results of both 1-DE and 2-DE followed by PMF, led to the identification of 24 virion proteins. Twenty new proteins, not yet identified by proteome analysis of closely related staphylococcal phages K and G1 were identified using this approach. Fifteen proteins were assigned unambiguously to the head-tail genome module; the remaining nine proteins are encoded by genes of the left or right arms of the phage genome. As expected, the most abundant proteins in the electrophoretic patterns are the major capsid protein, the major tail sheath protein and proteins identical to ORF 50 and ORF 95 of phage K, although their function is only putative. Identification of these 20 new proteins contributes substantially to a detailed characterization of phage virions, knowledge of which is necessary for rational phage therapy.     

Boric acid dust as a component of an integrated cockroach management program in confined swine production

Boric acid dust treatments were evaluated as a tool for the integrated management of the German cockroach, Blattella germanica (L.), in commercial confined swine production. The efficacy of boric acid dust was comparable to that of an organic residual insecticide, cyfluthrin, which is commonly used to control cockroaches in this environment. Fall treatments suppressed the cockroach population for longer durations than treatments in the Spring. Boric acid dust is an effective, inexpensive, and low risk (to animal and human health, and the environment) alternative for the management of cockroaches in livestock production systems.