Cavity cooling below the recoil limit

Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling.     

Asymmetric segregation of polarized antigen on B cell division shapes presentation capacity

During the activation of humoral immune responses, B cells acquire antigen for subsequent presentation to cognate T cells. Here we show that after mouse B cells accumulate antigen, it is maintained in a polarized distribution for extended periods in vivo. Using high-throughput imaging flow cytometry, we observed that this polarization is preserved during B cell division, promoting asymmetric antigen segregation among progeny. Antigen inheritance correlates with the ability of progeny to activate T cells: Daughter cells receiving larger antigen stores exhibit a prolonged capacity to present antigen, which renders them more effective in competing for T cell help. The generation of progeny with differential capacities for antigen presentation may have implications for somatic hypermutation and class switching during affinity maturation and as B cells commit to effector cell fates.     

Population genomics of early events in the ecological differentiation of bacteria

Genetic exchange is common among bacteria, but its effect on population diversity during ecological differentiation remains controversial. A fundamental question is whether advantageous mutations lead to selection of clonal genomes or, as in sexual eukaryotes, sweep through populations on their own. Here, we show that in two recently diverged populations of ocean bacteria, ecological differentiation has occurred akin to a sexual mechanism: A few genome regions have swept through subpopulations in a habitat-specific manner, accompanied by gradual separation of gene pools as evidenced by increased habitat specificity of the most recent recombinations. These findings reconcile previous, seemingly contradictory empirical observations of the genetic structure of bacterial populations and point to a more unified process of differentiation in bacteria and sexual eukaryotes than previously thought.     

An unusual outbreak of histomonosis in a commercial turkey flock

In the past histomonosis was very well controlled with Dimetridazole as a treatment and/or Nifursol as feed additive. In the European Union both products were banned in 1995 and 2003, respectively. This was followed by the re-emergence of the disease in the recent years. In the present case a farm with two houses was affected by the disease. In each house 2620 hens and 2620 toms were kept, separated by wire mesh. At the 53rd day of age the toms in house 1 showed general clinical symptoms, accompanied by a slightly raised mortality, which sharply increased in the following days. At necropsy all dead birds showed lesions typical for histomonosis in caeca and liver. Histomonosis was diagnosed by histopathology and PCR. Within five days cumulative mortality was 25.1%.The hens kept at the same house didn't show any symptoms. At day 57 two toms, which were kept in house 2, died and showed similar symptoms and lesions. Within the next three days 48 more birds died. Again the hens in house 2 showed neither clinical signs nor mortality. Treatment trials using herbal products and a change of litter directly after the onset of clinical signs did not reduce the mortality. On day 62 the toms of both houses were euthanized by CO2 in closed containers. The hens were kept until they were slaughtered in week 16 and did not show any evidence of histomonosis.     

Comparative spatiotemporal analysis of the intrathecal immune response in natural listeric rhombencephalitis of cattle and small ruminants

This study examined the spatiotemporal immune response in listeric rhombencephalitis of ruminants in situ. Our data support the view that astrocytes facilitate the containment of infectious lesions. Results on the natural disease recapitulate observations in experimental rodent models and suggest that the mounted adaptive lymphocytic response of ruminants is effective in eliminating Listeria monocytogenes (LM). However, our data indicate earlier participation of the adaptive immune response, a stronger B lymphocyte contribution and a more protracted macrophage infiltration in the natural disease than it has been deduced from experimental models. Therefore, such models should be complemented by studies in natural host systems. Various macrophage and microglia subsets are involved in listeric rhombencephalitis and their differential contribution may account for species differences in clinical course and outcome of infection as might species differences in the B-cell response. Future functional ex vivo and in vitro studies are necessary to further investigate the findings obtained in the present study.     

Multiple-locus variant-repeat assay (MLVA) is a useful tool for molecular epidemiologic analysis of Streptococcus agalactiae strains causing bovine mastitis

Group B streptococci (GBS) were considered a major cause of mastitis in cattle until preventive measures succeeded in controlling the disease in the 1970s and 1980s. During the last 5-6 years an increasing number of cases have been observed in some Scandinavian countries. A total of 187 GBS isolates from mastitis cases were collected from 119 animals in 34 Norwegian farms in the period from April 2007 to November 2010. 133 (71%) of the isolates were from farms with automated milking systems. The strains underwent typing of capsular polysaccharides (CPS) and surface proteins, and were analyzed by multi-locus variable repeat assay (MLVA) to investigate the epidemiological relationship of strains within and between farms. The GBS strains were differentiated into 12 types by CPS and surface protein analysis, with CPS types V (54%) and IV (34%) predominating. MLVA was superior to CPS and protein typing for strain differentiation, resolving the 187 strains into 37 types. In 29 of 34 farms all GBS strains had identical MLVA profiles specific for each farm. However, in one farm represented with 48 isolates, four MLVA variants with differences in one repeat locus were observed during the almost 3-year long collection period. Similar variations were observed at four other farms. This might reflect the stability of repeat loci under in vivo conditions. Farms with automated milking systems were overrepresented in this material. In conclusion, the five-loci MLVA allowed rapid high-resolution genotyping of the bovine GBS strains within and between farms.