Department of Biology, Acadia University, Wolfville, Nova Scotia, Canada B0P 1X0, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331.
Appl Environ Microbiol. 1990 Sep;56(9):2840-6. doi: 10.1128/aem.56.9.2840-2846.1990.
The ability of two octopine-catabolizing Pseudomonas spp. and two virulent octopine-type Agrobacterium tumefaciens to compete for substrates has been examined in chemostats. In dual cultures with octopine or glutamate as the limiting carbon or nitrogen source, Pseudomonas fluorescens B99A and E175D always dominated over A. tumefaciens B6 or ATCC 15955. The growth dynamics of each strain in pure culture indicated that some form of antagonism was occurring in dual culture to permit the predominance of the pseudomonads under certain conditions. Although both pseudomonads fluoresce, pyoverdine was not responsible for the observed inhibition. An unidentified antibiotic secreted by both pseudomonads is believed to be responsible. A. tumefaciens B6 grew synergistically in the presence of P. fluorescens B99A with octopine as the limiting nitrogen source. This behavior of Agrobacterium strain B6 may help overcome its grossly inefficient use of octopine as previously reported. The ability of these two pseudomonads to outcompete the agrobacteria under all conditions tested raises the possibility that under field conditions, infectious agrobacteria may be succeeded by opine-catabolizing pseudomonads around crown gall tumors and in the rhizosphere.
两种能够分解瓜氨酸的假单胞菌和两种具有毒性的瓜氨酸型根瘤农杆菌在恒化器中对底物的竞争能力已被研究。在以瓜氨酸或谷氨酸为限制碳源或氮源的双培养物中，荧光假单胞菌 B99A 和 E175D 总是比根瘤农杆菌 B6 或 ATCC 15955 占优势。每种菌株在纯培养中的生长动态表明，在某些条件下，双培养物中发生了某种形式的拮抗作用，从而允许假单胞菌占优势。尽管两种假单胞菌都发荧光，但并非是由于观察到的抑制作用是由绿脓菌素引起的。这两种假单胞菌分泌的一种未鉴定的抗生素被认为是造成这种情况的原因。根瘤农杆菌 B6 在以瓜氨酸为限制氮源的情况下与荧光假单胞菌 B99A 协同生长。根瘤农杆菌 B6 的这种行为可能有助于克服其先前报道的对瓜氨酸的低效利用。这两种假单胞菌在所有测试条件下都能够胜过根瘤农杆菌，这增加了一种可能性，即在田间条件下，传染性根瘤农杆菌可能会被冠瘿瘤周围和根际中分解瓜氨酸的假单胞菌所取代。
