Coupled ferric oxides and sulfates on the Martian surface

The Mars Exploration Rover (MER), Opportunity, showed that layered sulfate deposits in Meridiani Planum formed during a period of rising acidic ground water. Crystalline hematite spherules formed in the deposits as a consequence of aqueous alteration and were concentrated on the surface as a lag deposit as wind eroded the softer sulfate rocks. On the basis of Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) orbital data, we demonstrate that crystalline hematite deposits are associated with layered sulfates in other areas on Mars, implying that Meridiani-like ground water systems were indeed widespread and representative of an extensive acid sulfate aqueous system.     

Biological and DNA evidence of two dissimilar populations of the Rhipicephalus sanguineus tick group (Acari: Ixodidae) in South America

In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species.     

Long-term study of incidence and financial loss due to cattle babesiosis in an Argentinian dairy farm

The incidence and direct financial loss caused by babesiosis were evaluated in 121 Holstein Friesian female cattle that formed eight cohorts (1981–1988) of a dairy farm located approximately 24° 55′S 65° 29′W in Salta, Argentina. Female calves born in 1986 and 1987 (n=32) were vaccinated with a live Babesia vaccine at six months of age.

No cases of babesiosis occurred in the vaccinated cattle. The incidence of babesiosis in the six non-vaccinated cohorts was 23.6% (21/89). Eighteen of the cases were the result of Babesia bovis, one to Babesia bigemina and two to a mixed infection. Two cattle died of B. bovis infection in spite of drug treatment (diaminazene, 3.5 mg kg⁻¹). No disease occurred in cattle younger than seven months or older than 24 months. The number of cases according to age of cattle was: 7–9 months, 5; 10–12 months, 6; 13–24 months, 10.

Financial loss for the six cohorts that suffered clinical cases amounted to US $ 1624.6 (prices in October 1990)—62% were the result of physical losses and 38% to costs of control. A benefit-cost analysis of vaccination was carried out assuming that 95% of the mortality and morbidity losses of the six non-vaccinated cohorts was prevented after a single inculation of a live vaccine (cost of a dose plus administration was US $ 4.2. The benefit-cost ratio was 4:1 for each US dollar expended.     

Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data

Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the "siderikian") is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet.     

Sequence analysis of the msp4 gene of Anaplasma ovis strains

Anaplasma ovis (Rickettsiales: Anaplasmataceae) is a tick-borne pathogen of sheep, goats and wild ruminants. The genetic diversity of A. ovis strains has not been well characterized due to the lack of sequence information. In this study, we evaluated bighorn sheep (Ovis canadensis) and mule deer (Odocoileus hemionus) from Montana for infection with A. ovis by serology and sequence analysis of the msp4 gene. Antibodies to Anaplasma spp. were detected in 37% and 39% of bighorn sheep and mule deer analyzed, respectively. Four new msp4 genotypes were identified. The A. ovismsp4 sequences identified herein were analyzed together with sequences reported previously for the characterization of the genetic diversity of A. ovis strains in comparison with other Anaplasma spp. The results of these studies demonstrated that although A. ovismsp4 genotypes may vary among geographic regions and between sheep and deer hosts, the variation observed was less than the variation observed between A. marginale and A. phagocytophilum strains. The results reported herein further confirm that A. ovis infection occurs in natural wild ruminant populations in Western United States and that bighorn sheep and mule deer may serve as wildlife reservoirs of A. ovis.     

Analysis of world strains of Anaplasma marginale using major surface protein 1a repeat sequences

Anaplasma marginale is a tick-borne pathogen of cattle that causes the disease bovine anaplasmosis worldwide. Major surface proteins (MSPs) are involved in host-pathogen and tick-pathogen interactions and have been used as markers for the genetic characterization of A. marginale strains and phylogenetic studies. MSP1a is involved in the adhesion and transmission of A. marginale by ticks and varies among geographic strains in the number and sequence of amino-terminal tandem repeats. The aim of this study was to characterize the genetic diversity of A. marginale strains collected from countries in North and South America, Europe, Asia, Africa and Australia, inclusive of all continents. In this study, we characterized 131 strains of A. marginale using 79 MSP1a repeat sequences. These results corroborated the genetic heterogeneity of A. marginale strains in endemic regions worldwide. The phylogenetic analyses of MSP1a repeat sequences did not result in clusters according to the geographic origin of A. marginale strains but provided phylogeographic information. Seventy-eight percent of the MSP1a repeat sequences were present in strains from a single geographic region. Strong (> or =80%) support was found for clusters containing sequences from Italian, Spanish, Chinese, Argentinean and South American strains. The phylogenetic analyses of MSP1a repeat sequences suggested tick-pathogen co-evolution and provided evidence of multiple introductions of A. marginale strains from various geographic locations worldwide. These results contribute to the understanding of the genetic diversity and evolution of A. marginale and tick-pathogen interactions.     

Functional genomics and evolution of tick–Anaplasma interactions and vaccine development

The genus Anaplasma (Rickettsiales: Anaplasmataceae) includes several tick-transmitted pathogens that impact veterinary and human health. Tick-borne pathogens cycle between tick vectors and vertebrate hosts and their interaction is mediated by molecular mechanisms at the tick–pathogen interface. These mechanisms have evolved characteristics that involve traits from both the tick vector and the pathogen to insure their mutual survival. Herein, we review the information obtained from functional genomics and genetic studies to characterize the tick–Anaplasma interface and evolution of A. marginale and A. phagocytophilum. Anaplasma and tick genes and proteins involved in tick–pathogen interactions were characterized. The results of these studies demonstrated that common and Anaplasma species-specific molecular mechanism occur by which pathogen and tick cell gene expression mediates or limits Anaplasma developmental cycle and trafficking through ticks. These results have advanced our understanding of the biology of tick–Anaplasma interactions and have opened new avenues for the development of improved methods for the control of tick infestations and the transmission of tick-borne pathogens.     

Joint effects of biotic and abiotic stressors on winter wheat suppression of Bromus tectorum

In winter wheat systems in the Northern Great Plains of the United States, Bromus tectorum and wheat streak mosaic virus (WSMV) commonly co‐occur. While independent effects of these pests on wheat yields have been well documented, to our knowledge, no study has investigated whether WSMV modifies interactions between wheat and B. tectorum. Furthermore, the impact that environmental stressors such as nutrient availability have on these interactions has not been addressed. We conducted a randomised split‐plot field study over 2 years to investigate the effects of WSMV and nitrate (N) availability on winter wheat suppression of Bromus tectorum. The study included four N treatments (10–19, 20–31, 31–84, and 85–207 kg ha^?1) and two WSMV treatments (mechanically inoculated or control). Increasing soil N increased the susceptibility of wheat to WSMV infection. In 2009, wheat in the lowest and highest N levels had 24% and 65% of plants infected respectively. However, regression analysis indicated that interactive effects of wheat competition, N and WSMV did not play a consistent role in B. tectorum growth. Specifically, the effect of both wheat density and distance from row on B. tectorum biomass remained constant across inoculation treatments, suggesting that wheat inoculated with WSMV suppressed B. tectorum as effectively as healthy wheat. Furthermore, wheat had a greater impact on B. tectorum growth in higher N environments, even though incidence of WSMV infection in wheat was highest. Overall, our results suggest that WSMV infection may not change the ability of wheat to suppress B. tectorum.     

The effect of amino acids and amides on the regulation of nitrate uptake by wheat seedlings

Wheat plants grown hydroponically increased their nitrate uptake rate more than two‐fold after three days of N starvation. Exogenously supplied amino acids and amides had no effect on the nitrate uptake rate of plants well nourished in N. After three days of N starvation, however, some of the amino acids and amides supplied to plants inhibited up to 50% of the nitrate uptake rate. The most effective inhibitor was aspartic acid. Asparagine, glutamine or phenylalanine did not show any inhibitory effect. The percentage of inhibition was not increased by increasing the amino acid concentration, nor did the addition of mixed amino acids and amides increase the inhibition exerted by one amino acid alone. During the three days of N starvation, there was a decrease in the concentration of endogenous amino acids in the roots, but not all amino acids decreased their concentration at the same rate.

It is suggested that the endogenous levels of some amino acids may repress the nitrate uptake system in plants well supplied with N. During the development of the N deficiency, the concentration of these amino acid decreases, de‐repressing the nitrate uptake system.