Starvation and nonculturable state in plant-associated lactic acid bacteria

Lactobacillus plantarum P 5852 and Lactococcus lactis P 6010 entered a nonculturable state in response to starvation for essential nutrients in a laboratory microcosm. Starved cultures were resuscitated by addition of yeast extract or peptones plus vitamins, but they were not reactivated by the complete medium or glucose or vitamins alone. Investigations on plant exudates showed that amino-nitrogen as well as carbohydrates are excreted in very restricted amounts at certain times during the maturation of grass. The results are discussed in relation to the nonculturability of lactic acid bacteria colonizing plant surfaces and their consequent underestimation when enumerated by plate count methods.