Isolation and Identification of Bdellovibrio from Coastal Areas of Taiwan

Abstract

A survey of the occurrence and characteristics of Bdellovibrio around the coastal areas and aquacultural ponds of Taiwan was conducted. The recovery rate of bdellovibrios was highest in estuaries during summer. Prey-dependent Bdellovibrio sp. strain TS-S and strain TS-V were isolated from the estuary of the Tam-shui river, from which prey-independent strains were further selected by streptomycin treatment or by using enriched medium. Their mutation rates were 1.2×10-6 (streptomycin method) and 3.8×10-6 (enriched medium) for the strain TS-S and 1.1×10-5 (streptomycin method) and 2.1×10-6 (enriched medium) for the strain TS-V. Four prey-independent mutantswere isolated from strain TS-S by the enriched medium method and designated as Bdellovibrio sp. strains TS-SPI1 through TS-SPI4. Similarly, two prey-independent mutants, designated as TS-VPI1 and TS-VPI2, were obtained from strain TS-V. The physiological characteristics of these six prey-independent mutants differed from those of the three species (Bdellovibrio bacteriovorus, B. stolpii, and B. starrii), in comparisons by biochemical tests and electron microscopic examination. The average cell sizes of TS-SPIs and TS-VPIs, were 0.18×0.85 and 0.21×0.78 μm, respectively. These sizes are smaller than the cell sizes of the three species shown in Bergey's Manual.