Population dynamics and antagonistic potential of enterococci colonizing the phyllosphere of grasses

Abstract

Aims: To investigate the spatial and temporal dynamics of enterococci colonizing forage grass and their ability to produce bacteriocins. Methods and Results: Enterococci could be detected on above-ground plant parts throughout the growing season, with high continuity but low cell numbers (2á60´10 1 ± 6á16´10 4 cfu g ±1 fresh matter). A total of 750 strains were isolated and identi®ed by their whole-cell protein patterns as Enterococcus faecalis (7á9%), Ent. mundtii (7á9%), Ent. casseli¯avus (5á5%), Ent. faecium (5á2%) and Ent. sulfureus (0á1%). The vast majority of the strains (69á7%) formed a homogeneous 16S rDNA genotype that differed from those of known enterococci. A screening for antagonistic activity using an agar spot test revealed that 18á4% of all isolates were potential antagonists. Partially-puri®ed proteins extracted from cell-free culture supernatant uids of various species were characterized as pH-and heat-stable bacteriocins active against a wide range of lactic acid bacteria, clostridia and Listeria. The producing strains were antagonistically active even on`phylloplane agar' at temperatures between 4 and 37°C. Conclusions: Enterococci are a common part of the epiphytic micro¯ora of grasses, displaying probably some antagonistic activity. Signi®cance and Impact of the Study: The results provide new information on the distribution, species diversity and antagonistic potential of enterococci in the phyllosphere.

Enteroccoccus in Water, Sediment and Clams in a Tropical Environment,Maracaibo Lake, Venezuela

“…E. faecalis is the most common specie isolated from clinical samples (80-90%), interacts with many other organisms and has effects on the environment. In the other hand, E. casseliflavus has been reported in 20% of beach samples and it is associated with natural source, such as plants [31][32][33]. This is consistent with the results found in this research.…”

Enterococci in the Environment

“…Furthermore, the finding that certain strains of Enterococcus spp. may have environmental adaptations, for instance, E. casseliflavus in submerged aquatic vegetation (15) and E. casseliflavus, E. faecalis, E. faecium, E. hirae, E. mundtii, E. sulfureus, and many other strains resembling E. faecalis from forage crops (50,235,261), strongly supports the existence of plant-associated enterococci.…”

“…Recent studies have expanded these findings to forage and crop species (235,261). Mundt (237) initially suggested that the occurrence of enterococci in plants was seasonal, with maximum recovery in late summer (September), and that these bacteria were transient populations most likely introduced by insects and wind (237).…”

“…Mundt (237) initially suggested that the occurrence of enterococci in plants was seasonal, with maximum recovery in late summer (September), and that these bacteria were transient populations most likely introduced by insects and wind (237). Shortly thereafter, Mundt et al demonstrated the ability of E. faecalis to grow on plants (238), and many other studies have argued for the existence of epiphytic enterococci (204,235,261). Furthermore, the finding that certain strains of Enterococcus spp.…”

Mining into interspecific bacterial interactions

“…Natural bacterial populations have been found to consist of a wide variety of genotypes that differ in their ability to both suppress and withstand conspecifics (Ott et al, 2001;Riley et al, 2003;Davelos et al, 2004;Vos and Velicer, 2009). A trade-off between an advantage in growth (resource or scramble competition) and an advantage in 'killing capacity' or 'resistance capacity' (interference competition) lies at the basis of theoretical models attempting to explain the coexistence of strains differing in antibiotic production and sensitivity (Hsu and Waltman, 1997;Czaran and Hoekstra, 2003;Gardner and West, 2004;Czaran and Hoekstra, 2007;Brown et al, 2009;Hibbing et al, 2010).…”