Separation from whey of three growth factors for Streptococcus agalactiae.

Wheys of milk and colostrum were treated with ethanol and the concentrated supernatant fluids were subjected to chromatographic procedures (anion exchange resin, using distilled water as eluent). The fractions were tested for capabilities to stimulate the growth of Streptococcus agalactiae in a mixture (1:32) of pasteurized milk and steamed milk. Three stimulatory factors (F), designated F-1, F-2, and F-3, were separated; F-1 was nonionic, and F-2 and F-3 were cationic. A mixture containing any 2 factors gave greater stimulation than either factor tested alone, and a mixture of all 3 gave the greatest stimulation. The F-2 activity was attributed to cystine.     

Some observations on microbial populations and nitrogen in soils infested with the take-all fungus

Some possible causes of “take-all decline”, the decrease in the severity of attack by Gaeumannomyces graminis on cereals after several years' consecutive culture, are discussed. The possible relationships between the NO₃^?–N:NH₄⁺–N ratio in the rhizosphere, populations of rhizosphere bacteria and the incidence of take-all are considered.