An enhanced miniaturized assay for antimicrobial prospecting.

Bioprospecting for novel antimicrobials increasingly relies on extremely small samples unsuitable for conventional bulk extraction and assay. We developed a microtitre plate assay for minimal amounts of test materials which is rapid, extremely sensitive, allows time-course analysis and reduces false negatives. Developed for the analyses of antimicrobial sensitivity and resistance, the technique is appropriate for assays where source materials are scarce.

The timing of seed dispersal in Viooa nuttallii: attraction of dispersers and avoidance of predators.

Elaiosomes attract rodent predators, as well as ant dispersers (Myrmica discontinua and Formica podzolica), to Viola nuttallii seeds. Seed removal by ants and rodents was studied over 24 h and over two separate 4-h periods. Experimental treatments included i) ants and rodents having access to seeds, ii) only ants having access, iii) only rodents having access, and iv) neither ants nor rodents having access. Seed dehiscence was monitored for 3 days. A simple model is used to determine the relative importance of ants and rodents in removing seeds, and these frequencies are related to the time when most seeds were released. The data show that most seeds are shed from capsules between 9 AM and 1 PM and are immediately removed by ants. Ants, on the average, remove 88% of the seeds. The timing of seed dehiscence increases the probability of seeds being dispersed by ants. The results are discussed with respect to the hypothesis that a sychrony of the time of seed dispersal and the period when most ants (mutualists) and least rodents (predators) are active would be advantageous to the plant species.