Evaluation of cytogenetic effects of a naturally occurring non-ice-nucleation Pseudomonas fluorescens strain in Chinese hamster ovary (CHO) cells.

One of the main methods for eliminating ice-nucleation-active (INA+) bacteria, the micro-organisms responsible for frost injuries to plants at mild freezing temperatures, is the use, as competitors, of other naturally occurring non-nucleating strains (non-INA). In the present article we investigated the cytogenetic effects of a naturally occurring non-INA strain of Pseudomonas fluorescens (MS 1640 R3), evaluating the induction of chromosomal aberrations and sister chromatid exchanges (SCEs) in Chinese hamster ovary (CHO) cells in the absence and presence of rat S9 metabolism. The results obtained did not show any increase in either chromosomal aberrations or SCEs, both in the absence and presence of rat S9 metabolism when used as (i) intact bacteria cells, (ii) sonicated bacteria (i.e., potential endotoxins), or (iii) metabolic bacterial products (i.e., potential exotoxins) released in the growth medium. © 1995 Wiley-Liss, Inc.