Abstract: Methods, devices, and systems are disclosed for collecting or gathering samples, such as zebrafish or zebrafish eggs or embryos, dispersed in a liquid and transferring the collected or gathered samples into discrete receptacles of a holding fixture (e.g. the wells of a multi-well plate, a Petri dish, or any other suitable fixture having one or more receptacles). A method includes drawing some of the liquid through a plurality of openings in a retention structure so as to draw at least some of the samples into contact with associated openings, retaining the samples in contact with the retention structure adjacent to the associated openings using differential pressure, moving at least one of the retention structure or a holding fixture relative to the other while the samples are retained adjacent the associated openings, and ejecting samples from the retention structure into associated discrete receptacles of the holding fixture.

Abstract: Disclosed are virulent or opportunistic prokaryotes in which metal ion-dependent gene regulation confers a growth or an infectious advantage. The prokaryote contains a DNA molecule containing a sequence encoding a dominant, metal ion-independent repressor protein or a partially metal-ion independent repressor protein. The prokaryotes are formulated into vaccine compositions and administered to a human or other animal to enhance protective immunity against infectious and diseases caused by prokaryotes in which metal ion-dependent gene regulation confers a growth or an infectious advantage.