A soil-based microbial biofilm exposed to 2,4-D: bacterial community development and establishment of conjugative plasmid pJP4

Abstract

A soil suspension was used as a source to initiate the development of microbial communities in flow cells irrigated with 2,4-dichlorophenoxyacetic acid (2,4-D) (25 microg ml(-1)). Culturable bacterial members of the community were identified by 16S rRNA gene sequencing and found to be members of the genera Pseudomonas, Burkholderia, Collimonas and Rhodococcus. A 2,4-D degrading donor strain, Pseudomonas putida SM1443 (pJP4::gfp), was inoculated into flow cell chambers containing 2-day old biofilm communities. Transfer of pJP4::gfp from the donor to the bacterial community was detectable as GFP fluorescing cells and images were captured using confocal scanning laser microscopy (GFP fluorescence was repressed in the donor due to the presence of a chromosomally located lacI(q) repressor gene). Approximately 5-10 transconjugant microcolonies, 20-40 microm in diameter, could be seen to develop in each chamber. A 2,4-D degrading transconjugant strain was isolated from the flow cell system belonging to the genus Burkholderia.

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

“…Hausner and Wüertz found that the plasmid transfer rate quantified by in situ image analysis was 1,000-fold higher than that determined by classical plating techniques (31), and similar results were obtained in other studies (39,65). A combination of standard plating and fluorescence microscopy has been used to monitor transfer of the IncP-9 plasmid pWW0 (12,14,30,53,62), the IncP-1 plasmids pRK415 (31) and pJP4 (5), the IncX1 plasmid pMAS2027 (54), and the novel unclassified plasmids pQBR11 (47) and pBF1 (19) in biofilms grown under different experimental conditions. Interestingly, plasmid transfer has often been shown to be limited to the surfaces of colonies or biofilms, and complete plasmid invasion has not been observed (12,14,30).…”

“…They code for short rigid sex pili and have been observed to transfer at higher rates between cells growing on solid surfaces than between those in liquids (9), in part due to shear forces in liquids that hinder the formation and stability of mating pairs (70). Few studies have monitored the spread of IncP-1 plasmids in biofilms (3,5,31,48), and to the best of our knowledge, virtually nothing is known about the factors that affect their transfer efficiency in this important environment.…”

The bacterial genus Collimonas: mycophagy, weathering and other adaptive solutions to life in oligotrophic soil environments

“…Culturable collimonads have been isolated on several types of media (Table 1), but with a clear bias towards those that mimic oligotrophic conditions, such as R2A (Aspray et al ., 2005) and diluted tryptic soy agar (Axelrood et al ., 2002), mineral medium supplemented with a single carbon/energy source (Wilson et al ., 2003), and chitin‐yeast extract agar (de Boer et al ., 1998b; Höppener‐Ogawa et al ., 2007). None of these media is truly Collimonas ‐specific, meaning that they are weak predictors of Collimonas identity for the bacterial colonies that they sustain.…”

Bacterial mycophagy: definition and diagnosis of a unique bacterial–fungal interaction

“…By way of prediction, we would expect that bacterial mycophagy plays a more prominent role in fungus‐featuring environments that are otherwise characterized by low alternative nutrient availability. Indeed, culturable representatives from the mycophagous genus Collimonas have been isolated from nutrient‐poor soils such as from the dunes on the island of Terschelling, the Netherlands (de Boer et al ., 2001, 2004), and from natural grassland and heathland (Höppener‐Ogawa et al ., 2007) but also forest soils (Aspray et al ., 2005; Mannisto & Haggblom, 2006).…”