FIG. 1.

Seasonal variation in persistence in situ and in the laboratory. Feces were dispersed in raw river water, duplicate 30-ml portions were incubated in diffusion chambers in the river or in flasks in the laboratory, and daily samples were assayed for the presence of B. distasonis by PCR and dot blot hybridization as described in the text. Samples were taken before addition of feces (−), immediately after addition of feces (day 0), and after incubation for 1 to 5 days. Experiments ran from 24 to 29 April (rows a and b), from 5 to 10 May (rows c and d), from 6 to 11 June (rows e to h), and from 6 to 13 July (rows i to l), all in 1995. Surface water temperatures in the river were 14, 14, 22 to 24, and 26 to 28°C, respectively. Rows a, b, e, f, i, and j are samples taken from diffusion chambers incubated in the river. Rows c, d, g, h, k, and l are samples from flasks incubated in the laboratory at the indicated temperatures.