Bahat-Samet et al. (2004) stated that aggregation is important in the production, storage and survival of agriculturally important bacterial inoculants. Aggregation can also be induced by changes in the nutrients of culture media in which bacterial cells are grown (Sadasivan and Neyra, 1985 and Burdman et al., 1999) or by addition of various inducing agents (Joe et al., 2009). Hence, studies on the ability of bacteria to co-aggregate with other and the effect of various physical and chemical factors on the stability of co-aggregation is of great significance before effective formulation for field applications can be made.