Rosenberg E, Keller K H, Dworkin M
J Bacteriol. 1977 Feb;129(2):770-7. doi: 10.1128/jb.129.2.770-777.1977.
When Myxococcus xanthus FB was grown on 0.2% casein it exhibited a phenomenon we call cooperative growth. That is, above 104 cells per ml, both strains that were studied exhibited increasing growth rates as a function of increasing cell numbers. Between 104 and 107 cells per ml, the mean doubling times of strains YS and TNS decreased from 15.2 to 8 h and 26 to 8.5 h, respectively. The extracellular proteinase activity of the two strains was equivalent and directly proportional to cell number. Cooperative growth was correlated with increased concentration of hydrolyzed casein in the medium, suggesting cooperative hydrolysis of casein. At low cell densities neither strain was capable of measurable growth on casein in liquid media, and we have calculated that the average concentration of hydrolyzed casein in the medium was indeed too low to support growth. At low cell densities, growth on hydrolyzed casein (Casitone) was normal and independent of cell concentration. Demonstration of cooperative growth at higher cell densities supports the suggestion that the communal behavior of myxobacteria results in more efficient feeding.
当黄色粘球菌FB在0.2%的酪蛋白上生长时，它表现出一种我们称之为协同生长的现象。也就是说，当每毫升细胞数超过10⁴个时，所研究的两种菌株的生长速率均随细胞数量的增加而提高。在每毫升10⁴至10⁷个细胞之间，YS和TNS菌株的平均倍增时间分别从15.2小时降至8小时以及从26小时降至8.5小时。这两种菌株的胞外蛋白酶活性相当，且与细胞数量成正比。协同生长与培养基中水解酪蛋白浓度的增加相关，这表明酪蛋白存在协同水解作用。在低细胞密度下，两种菌株在液体培养基中的酪蛋白上均无法实现可测量的生长，并且我们计算得出培养基中水解酪蛋白的平均浓度确实过低，无法支持生长。在低细胞密度下，在水解酪蛋白（酪蛋白胨）上的生长是正常的，且与细胞浓度无关。在较高细胞密度下协同生长的证明支持了这样一种观点，即粘细菌的群体行为导致更高效的摄食。
