Convergent incidences of Wolbachia infection in fig wasp communities from two continents

Wide surveys suggest that Wolbachia bacteria infect ca. 20% of all insect species, but particular taxonomic or ecological groups may display significantly higher or lower incidences. We studied 61 fig wasp species in Australia and found the highest known incidence (67%) of infection in a targeted study of this nature. A comparable study in Panama reported a similar figure (59%), confirming the exceptionally high incidence of Wolbachia in fig wasps. Importantly, these are two independent estimates of Wolbachia incidence in fig wasp communities, because no host species, or even genera, are shared between localities. The high level of infection may reflect enhanced opportunities for horizontal transmission inside fig fruits. Although incidence was similar in Panama and Australia, the actual strains involved were different and region-specific. Local strains were shared by several host species, although there was often no obvious (direct) ecological link between two hosts with the same infection.     

Deep mtDNA divergences indicate cryptic species in a fig-pollinating wasp

Background  

Figs and fig-pollinating wasps are obligate mutualists that have coevolved for ca 90 million years. They have radiated together, but do not show strict cospeciation. In particular, it is now clear that many fig species host two wasp species, so there is more wasp speciation than fig speciation. However, little is known about how fig wasps speciate.     

Horizontal transmission of Wolbachia in a Drosophila community

Abstract.  1.  Wolbachia bacteria are reproductive parasites of arthropods and infect an estimated 20% of all insect species worldwide. In order to understand patterns of Wolbachia infection, it is necessary to determine how infections are gained or lost. Wolbachia transmission is mainly vertical, but horizontal transmission between different host species can result in new infections, although its ecological context is poorly understood. Horizontal transmission is often inferred from molecular phylogenies, but could be confounded by recombination between different Wolbachia strains.
2. This study addressed these issues by using three genes: wsp , ftsZ , and groE , to study Wolbachia infections in fruit- and fungus-feeding Drosophila communities in Berkshire, U.K.
3. Identical sequences were found for all three genes in Drosophila ambigua and Drosophila tristis. This suggests horizontal transmission of Wolbachia between these two previously unstudied Drosophila species, which may be the result of the two host species sharing the same food substrates or parasites.
4.  Wolbachia infections might be lost from species due to curing by naturally occurring antibiotics and the presence of these is likely to vary between larval food substrates.
5. It was investigated whether Wolbachia incidence was lower in fungus-feeding than in fruit-feeding Drosophila species, but no significant difference based on food substrate was found.     

FtcR is a new master regulator of the flagellar system of Brucella melitensis 16M with homologs in Rhizobiaceae

The flagellar regulon of Brucella melitensis 16M contains 31 genes clustered in three loci on the small chromosome. These genes encode a polar sheathed flagellum that is transiently expressed during vegetative growth and required for persistent infection in a mouse model. By following the expression of three flagellar genes (fliF, flgE, and fliC, corresponding to the MS ring, hook, and filament monomer, respectively), we identified a new regulator gene, ftcR (flagellar two-component regulator). Inactivation of ftcR led to a decrease in flagellar gene expression and to impaired Brucella virulence. FtcR has a two-component response regulator domain as well a DNA binding domain and is encoded in the first flagellar locus of B. melitensis. Both the ftcR sequence and its genomic context are conserved in other related alpha-proteobacteria. During vegetative growth in rich medium, ftcR expression showed a peak during the early exponential phase that paralleled fliF gene expression. VjbR, a quorum-sensing regulator of the LuxR family, was previously found to control fliF and flgE gene expression. Here, we provide some new elements suggesting that the effect of VjbR on these flagellar genes is mediated by FtcR. We found that ftcR expression is partially under the control of VjbR and that the expression in trans of ftcR in a vjbR mutant restored the production of the hook protein (FlgE). Finally, FtcR binds directly to the upstream region of the fliF gene. Therefore, our data support the role of FtcR as a flagellar master regulator in B. melitensis and perhaps in other related alpha-proteobacteria.     

Aphid moulting under controlled electrical conditions

The moulting of MYZUS PERSICAE under constant conditions of temperature, light (200 w filament light-bulb, d.c.) and almost constant relative humidity was studied. Maxima of moulting, counted at one-hour intervals between 12:00 and 15:00 hr under shielded conditions, could be traced more clearly when the air exchange in the shielded room was avoided. In electrical fields, to which the populations were exposed for 15–20 min, depressions of moulting numbers could be observed with relatively high electrical intensities (10 v),an increase, with medium electrical intensities (1 v), and a delayed increase of moulting with low intensities (0.1 v).Increases of moulting figures in comparison to the daily mean were also found in air negatively ionized (10–20 min application) by means of both high voltage corona discharge and radioactive tritium. It was found, that activity changes in the aphids (increase of moulting) often took place with a sudden rise of negative air ion density or with a drastic reduction of high positive air ion concentration.

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Zusammenfassung MYZUS PERSICAE-HÄutungen in konstantem Licht (200 Watt-Glühbirne,Gleichstrom),konstanter Temperatur und annÄhernd konstanter relativer Luftfeuchtigkeit wurden stündlich ausgezÄhlt.Die unter verschieden abgeschirmten Bedingungen festgestellten HÄutungsmaxima zwischen 12:00–15:00 h traten klarer zutage,wenn die abgeschirmte Kabine hermetisch geschlossen wurde. In künstlich erzeugten elektrischen Feldern schienen höhere elektrische IntensitÄten (10 v) eine Depression, mittlere (1 v)HÄutungszunahme zu ergeben, die bei niedrigen FeldstÄrken (0,1 v) mit einstündiger VerspÄtung in Erscheinung trat. Relative HÄutungszunahmen (Mittelwertgegenüberstellungen) waren auch nach künstlicher negativer Ionisation der Luft mit Hilfe der stillen Corona-Entladung oder einer radioaktiven Tritium-Quelle festzustellen.Die beobachteten HÄutungsanstiege fielen dabei zeitlich sowohl mit plötzlichem, starkem Ansteigen negativer als auch mit drastischer Verminderung hoher positiver Ionenkonzentrationen zusammen.

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Résumé Les mues de MYZUS PERSICAE en lumière (ampoule electrique, courant continu, 200 Watt), temperature constante et humidité relative de l'air approximativement constante ont été comptées une fois par heure.Les maximas de midi entre 12.00–15.00 h, constatés sous des conditions d'écran differents se montraient plus nettes si la cabine écran était hermetiquement fermé. Il semblait que dans des champs électriques artificiels des intensités de champ plus grandes (10 v) provoquent une dépression, des intensités moyennes (1 v) par contre une augmentation du nombre de mues — qui ne se montraient qu'après une heure de retard si l'intensité du champ était petite (0,1 v).De mÊme on constatait souvent une augmentation relative des mues (comparaison des valeurs moyennes) après une ionisation négative artificielle de l'air à l'aide d'une décharge corona,ainsi qu'à l'aide d'une source radioactive de Tritium. Les augmentation du nombre de mues observées coÏncidaient aussi bien avec une augmentation abrupte et forte de la concentration d'ions négatifs qu'avec une diminution frappante de la concentration d'ions positifs.

     

Temporal patterns in immune responses to a range of microbial insults (Tenebrio molitor)

Much work has elucidated the pathways and mechanisms involved in the production of insect immune effector systems. However, the temporal nature of these responses with respect to different immune insults is less well understood. This study investigated the magnitude and temporal variation in phenoloxidase and antimicrobial activity in the mealworm beetle Tenebrio molitor in response to a number of different synthetic and real immune elicitors. We found that antimicrobial activity in haemolymph increased rapidly during the first 48h after a challenge and was maintained at high levels for at least 14 days. There was no difference in the magnitude of responses to live or dead Escherichia coli or Bacillus subtilis. While peptidoglylcan also elicited a long-lasting antimicrobial response, the response to LPS was short lived. There was no long-lasting upregulation of phenoloxidase activity, suggesting that this immune effector system is not involved in the management of microbial infections over a long time scale.     

Reinvestigation of potato starch volume during the sorption process

A thorough reinvestigation of the dependence of the specific volume of potato starch on water ad- and desorption is described. Measurements by toluene pycnometry show that hysteresis only occurs between 0 and 13% H₂O (dry solids basis). The results are interpreted in terms of a progressive filling of intergranular voids by water molecules of equivalent constant density. Other results give information on bulk starch density, thermal expansion coefficients, the influence of different immersion liquids and the effect of the different physical states of starchy products (dry gels and acid hydrolysed fractions).