Impact of the Microscale Distribution of a Pseudomonas Strain Introduced into Soil on Potential Contacts with Indigenous Bacteria

Abstract

Soil bioaugmentation is a promising approach in soil bioremediation and agriculture. Nevertheless, our knowledge of the fate and activity of introduced bacteria in soil and thus of their impact on the soil environment is still limited. The microscale spatial distribution of introduced bacteria has rarely been studied, although it determines the encounter probability between introduced cells and any components of the soil ecosystem and thus plays a role in the ecology of introduced bacteria. For example, conjugal gene transfer from introduced bacteria to indigenous bacteria requires cell-to-cell contact, the probability of which depends on their spatial distribution. To quantitatively characterize the microscale distribution of an introduced bacterial population and its dynamics, a gfp-tagged derivative of Pseudomonas putida KT2440 was introduced by percolation in repacked soil columns. Initially, the introduced population was less widely spread at the microscale level than two model indigenous functional communities: the 2,4-dichlorophenoxyacetic acid degraders and the nitrifiers (each at 10 6 CFU g ؊1 soil). When the soil was percolated with a substrate metabolizable by P. putida or incubated for 1 month, the microscale distribution of introduced bacteria was modified towards a more widely dispersed distribution. The quantitative data indicate that the microscale spatial distribution of an introduced strain may strongly limit its contacts with the members of an indigenous bacterial community. This could constitute an explanation to the low number of indigenous transconjugants found most of time when a plasmid-donor strain is introduced into soil.

Broad host range plasmids can invade an unexpectedly diverse fraction of a soil bacterial community

“…In soil, physical barriers limit contact between freshly introduced plasmid donors and potential recipients (Dechesne et al, 2005); here we maximized cell-tocell contact in a gene transfer assay (Musovic et al, 2010) to study the intrinsic permissiveness of the recipient community. All three plasmids (RP4, pIPO2tet and pKJK5) were introduced to the soil community in matings with a Pseudomonas putida donor strain, whereas plasmid pKJK5 was also introduced via E. coli and Kluyvera sp.…”

Microbial Resource Management: The Road To Go for Environmental Biotechnology

“…The aspects of movement and transport of microorganisms in air, water and particularly in soil are crucial in the context of genetic exchange [34], biodiversity (see further), and coordi-nated functioning such as for instance that of ammonium oxidizing and nitrite oxidizing bacteria [35]. For instance, we need to deal with phenomena of mobility and chemotaxis and consequently the spatial and temporal changes as they occur between cells in a 3D microsite.…”

Dynamics of augmented soil system containing biphenyl with Dyella ginsengisoli LA-4

“…Bioaugmentation by inoculated specific compounds degraders, which help conventional biodegradation processes run faster, is expected as the most straightforward strategy to remedy such systems [7]. Bioaugmentation has been used as a tool for bioremediation of xenobiotic-contaminated soil [6,8,9].…”