Responses of soil nitrite-oxidizers to global environmental changes

Background/Question/Methods
There is increasing evidence that global change can alter the structure of plant
communities with large impacts on the functioning of terrestrial ecosystems. However, little is known about the impact of global change on soil microbial communities. In particular, the response of soil nitrite-oxidizers microorganisms that mediate the second step of nitrification, a key process of the nitrogen cycle, has never been investigated.
Here, we examined the effects of four main global environmental changes on the activity, the abundance and the diversity of soil nitrite-oxidizers in an annual grassland ecosystem as part of the Jasper Ridge Global Change Experiment (CA, USA). This experiment includes four treatments - CO2, temperature, precipitation and nitrogen - with two levels per treatment (ambient and elevated, with elevated treatment based on prediction for the end of the century), and all of their factorial combinations. We measured potential nitrite oxidation, the abundance of soil Nitrobacter- and Nitrospiralike nitrite-oxidizers (using quantitative PCR targeting nxrA and 16S rRNA gene, respectively) and the diversity of soil Nitrobacter-like nitrite-oxidizers (using cloning sequencing targeting the nxrA gene) in each treatment combination at the end of the 7th and 8th growing seasons under treatments. Furthermore, we analyzed to what extent changes in the activity of the soil nitrite-oxidizers result from changes in their abundance or diversity.

Results/Conclusions
Simulated global environmental changes significantly altered the activity, as well as the abundance and the diversity of soil nitrite-oxidizers. Potential nitrite oxidation decreased with increased precipitation and increased with elevated CO2 when combined with added nitrogen or precipitation. The abundance of soil Nitrobacter-like nitrite-oxidizers also decreased with increased precipitation and increased with elevated levels of CO2 and nitrogen. In contrast, the abundance of soil Nitrospira-like nitrite-oxidizers increased with enhanced precipitation and decreased with elevated levels of CO2 and temperature. Finally, the structure of the soil Nitrobacter-like nitrite-oxidizers was significantly altered by the treatments. Consistent with results reported by Attard et al. (2010) for agroecosystems, we found that changes in potential rates of nitrite oxidation in response to treatments were partly explained by changes in the abundance of soil Nitrobacter-like nitrite-oxidizers, but not by changes in the abundance of soil Nitrospiralike nitrite-oxidizers, suggesting that Nitrobacter-like nitrite-oxidizers were the main functional players of the soil nitrite-oxidizing microbial community.
Our study provides evidence that global change could alter the abundance and diversity of soil nitrite-oxidizers, with potential impacts for soil nitrogen cycling.

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Direct and indirect measurement of somatic cell count as indicator of intramammary infection in dairy goats

<p>Abstract</p> <p>Background</p> <p>Mastitis is the most important and costly disease in dairy goat production. Subclinical mastitis is common in goats and is mainly caused by contagious bacteria. Several methods to diagnose subclinical mastitis are available. In this study indirect measurement of somatic cell count (SCC) by California Mastitis Test (CMT) and direct measurement of SCC using a portable deLaval cell counter (DCC) are evaluated. Swedish goat farmers would primarily benefit from diagnostic methods that can be used at the farm. The purpose of the study was to evaluate SCC measured by CMT and DCC as possible markers for intramammary infection (IMI) in goats without clinical symptoms of mastitis. Moreover to see how well indirect measurement of SCC (CMT) corresponded to direct measurement of SCC (DCC).</p> <p>Method</p> <p>Udder half milk samples were collected once from dairy goats (n = 111), in five different farms in Northern and Central Sweden. Only clinically healthy animals were included in the study. All goats were in mid to late lactation at sampling. Milk samples were analyzed for SCC by CMT and DCC at the farm, and for bacterial growth at the laboratory.</p> <p>Results</p> <p>Intramammary infection, defined as growth of udder pathogens, was found in 39 (18%) of the milk samples. No growth was found in 180 (81%) samples while 3 (1%) samples were contaminated. The most frequently isolated bacterial species was coagulase negative staphylococci (CNS) (72% of all isolates), followed by <it>Staphylococcus aureus </it>(23% of all isolates). Somatic cell count measured by DCC was strongly (p = 0.000) associated with bacterial growth. There was also a very strong association between CMT and bacterial growth. CMT 1 was associated with freedom of IMI while CMT ≥2 was associated with IMI. Indirect measurement of SCC by CMT was well correlated with SCC measured by DCC.</p> <p>Conclusions</p> <p>According to the results, SCC measured with CMT or DCC can predict udder infection in goats, and CMT can be used as a predictor of the SCC.</p

Reduced Lentivirus Susceptibility in Sheep with TMEM154 Mutations

Visna/Maedi, or ovine progressive pneumonia (OPP) as it is known in the United States, is an incurable slow-acting disease of sheep caused by persistent lentivirus infection. This disease affects multiple tissues, including those of the respiratory and central nervous systems. Our aim was to identify ovine genetic risk factors for lentivirus infection. Sixty-nine matched pairs of infected cases and uninfected controls were identified among 736 naturally exposed sheep older than five years of age. These pairs were used in a genome-wide association study with 50,614 markers. A single SNP was identified in the ovine transmembrane protein (TMEM154) that exceeded genome-wide significance (unadjusted p-value 3×10−9). Sanger sequencing of the ovine TMEM154 coding region identified six missense and two frameshift deletion mutations in the predicted signal peptide and extracellular domain. Two TMEM154 haplotypes encoding glutamate (E) at position 35 were associated with infection while a third haplotype with lysine (K) at position 35 was not. Haplotypes encoding full-length E35 isoforms were analyzed together as genetic risk factors in a multi-breed, matched case-control design, with 61 pairs of 4-year-old ewes. The odds of infection for ewes with one copy of a full-length TMEM154 E35 allele were 28 times greater than the odds for those without (p-value<0.0001, 95% CI 5–1,100). In a combined analysis of nine cohorts with 2,705 sheep from Nebraska, Idaho, and Iowa, the relative risk of infection was 2.85 times greater for sheep with a full-length TMEM154 E35 allele (p-value<0.0001, 95% CI 2.36–3.43). Although rare, some sheep were homozygous for TMEM154 deletion mutations and remained uninfected despite a lifetime of significant exposure. Together, these findings indicate that TMEM154 may play a central role in ovine lentivirus infection and removing sheep with the most susceptible genotypes may help eradicate OPP and protect flocks from reinfection

Les infections mammaires a lentivirus chez les Petits Ruminants

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 84738 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Infection of primary cultures of mammary epithelial cells by small ruminant lentiviruses

International audienc

RT-PCR detection of lentiviruses in milk or mammary secretions of sheep or goats from infected flocks

Using Smart Source ParsingIn this study we evaluated a reverse transcriptase polymerase chain reaction (RT-PCR) technique for detecting lentiviral infection in milk or mammary secretions from small ruminants. Initial observations on seven goats infected with cloned caprine arthritis-encephalitis virus (CAEV) showed that RT-PCR on milk cells is as reliable as coculture for detecting viral infection, and is quicker and simpler. With a suitable choice of redundant primers followed by a semi-nested amplification, it proved possible to detect the virus in milk samples from naturally infected French sheep (8/8) or goats (9/9), and viral sub-groups could be identified by hybridization with discriminatory probes. All seropositive animals gave positive amplifications, as did one seronegative goat from a contaminated herd, suggesting greater sensitivity for RT-PCR. None of eight goats from a long-established seronegative herd ever gave a positive RT-PCR amplification. This technique provides a simple means for rapidly identifying potentially infectious animals and for epidemiological investigations, as long as the primers are selected according to the genetic structure of the local viral population