Note on occurrence of Mymaromella pala Huber and Gibson (Hymenoptera: Mymarommatidae) in Montana: a new state record

The parasitic wasp Mymaromella pala Huber and Gibson (Hymenoptera: Mymarommatidae) was collected at 4 sites within a canyon reach of the Kootenai River in Lincoln County, Montana. This minute species has only recently been described, but it appears to have a large distribution throughout the United States and to be associated with upland and riparian forests. La avispa parasitaria Mymaromella pala Huber y Gibson (Hymenoptera: Mymarommatidae) se recolectó en cuatro sitios a lo largo de un cañón del Río Kootenai en Lincoln Co., MT. Hace poco que se describió esta especie diminuta, pero parece tener una distribución extensa en los EE.UU. y estar asociada con bosques altos y ribereños.     

Pilus retraction powers bacterial twitching motility

Twitching and social gliding motility allow many gram negative bacteria to crawl along surfaces, and are implicated in a wide range of biological functions. Type IV pili (Tfp) are required for twitching and social gliding, but the mechanism by which these filaments promote motility has remained enigmatic. Here we use laser tweezers to show that Tfp forcefully retract. Neisseria gonorrhoeae cells that produce Tfp actively crawl on a glass surface and form adherent microcolonies. When laser tweezers are used to place and hold cells near a microcolony, retractile forces pull the cells toward the microcolony. In quantitative experiments, the Tfp of immobilized bacteria bind to latex beads and retract, pulling beads from the tweezers at forces that can exceed 80 pN. Episodes of retraction terminate with release or breakage of the Tfp tether. Both motility and retraction mediated by Tfp occur at about 1 microm s(-1) and require protein synthesis and function of the PilT protein. Our experiments establish that Tfp filaments retract, generate substantial force and directly mediate cell movement.     

Untersuchungen an Bariumtitanat-Einkristallen

Summary It was possible to produce bariumtitanate monocrystals with ferroelectric qualities, which is shown in the temperature curve of the dielectric constant, in the resonance frequency, and also in hysteresis phenomena.     

A lytic factor associated with brucellaphage causing ‘lysis-from-without’

Résumé Des bactériophages de Brucella se sont montrés capables de provoquer une lyse extra-cellulaire, en cultures liquides deB. abortus, en présence de glycine et d'acide éthylène-diamine-tétraacétique. Des traitements au sérum anti-bactériophage, aux enzymes protéolytiques, ou la centrifugation différentielle dans le chlorure de césium n'ont pu séparer l'activité lytique de la particule infectieuse elle-même.

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This study was supported by Public Health Service research grant No. AI 06161 from the National Institute of Allergy and Infectious Diseases and by a World Health Organization research grant. The authors are grateful to Dr.D. Pratt for helpful suggestions and assistance with the density gradient centrifugation.