Colonization of soil by Arthrobacter and Pseudomonas under varying conditions of water and nutrient availability as studied by plate counts and transmission electron microscopy

Abstract

Arthrobacter globiformis and a Pseudomonas soil isolate were incubated separately and in combination in soil that had been presterilized by autoclaving. Growth and other responses of the cells in situ in this soil were monitored by plate counts and transmission electron microscopy examinations of cell sections. During the soil incubations, some of the samples were first allowed to dry and then were remoistened with water or with a dilute or a concentrated nutrient solution. Based on plate counts and ultrastructural analyses, Arthrobacter seemed to be in a non-multiplying coccoid-rod resting state and to be virtually immune to soil drying. Addition of a dilute nutrient solution helped maintain cell ultrastructure and prevent a low level of lysing that occurred in the absence of nutrient addition. Addition of a concentrated nutrient solution brought on cell multiplication as both coccoid-rods and long rods, but the ultimate form with further incubation was the coccoid-rod. The Pseudomonas strain suffered death and ultrastructural deterioration as water became less available. It responded by cell multiplication to an equal extent when either water or dilute nutrients were added, but possibly was able to give a growth response to nutritive amendment when a concentrated nutrient addition was made. The Arthrobacter was not affected by the presence ofPseudomonas in dual culture. The Pseudomonas, however, possibly suffered a nutritive deficiency under these conditions.

Survival of Pseudomonas fluorescens and Bacillus subtilis introduced into two soils of different texture in field microplots

“…The dynamics of P. fluorescens (Figs. 2 and 3) was consistent with previous data on introduced fluorescent pseudomonads in soil [32][33][34]. The better survival in the silt loam was consistent with the hypothesis that in finer-textured, clay-type soils micro-organisms are better protected against harsh soil conditions than in coarser, sandy soils [351.…”

Changes in the phyllosphere community of the resurrection fern, Polypodium polypodioides, associated with rainfall and wetting

“…Many other isolates were related to known plant-associated bacteria, including Bacillus cereus/ Bacillus thuringiensis and Arthrobacter sp. Some species of Arthrobacter can tolerate desiccation (Labeda et al, 1976) and the presence of these bacteria on both wet and dry fern suggests that the isolates obtained in this study might have similar capabilities. Other isolates related to known plant symbionts included species of Curtobacterium and Pseudomonas.…”

Isolation of Arthrobacter species from the phyllosphere and demonstration of their epiphytic fitness

“…), for example desiccation tolerance (Labeda et al. ), contributed to the ability of A6 and the cp isolates to deal with and rebound from the imposed stress of low relative humidity on leaf surfaces (Fig. ).…”