Role of flagella and type four pili in the co-migration of Burkholderia terrae BS001 with fungal hyphae through soil

Abstract

Burkholderia terrae BS001 has previously been found to be able to disperse along with growing fungal hyphae in soil, with the type-3 secretion system having a supportive role in this movement. In this study, we focus on the role of two motility- and adherence-associated appendages, i.e. type-4 pili (T4P) and flagella. Electron microcopy and motility testing revealed that strain BS001 produces polar flagella and can swim on semi-solid R2A agar. Flagellum- and T4P-negative mutants were then constructed to examine the ecological roles of the respective systems. Both in liquid media and on swimming agar, the mutant strains showed similar fitness to the wild-type strain in mixed culture. The flagellar mutant had completely lost its flagella, as well as its swimming capacity. It also lost its co-migration ability with two soil-exploring fungi, Lyophyllum sp. strain Karsten and Trichoderma asperellum 302, in soil microcosms. In contrast, the T4P mutant showed reduced surface twitching motility, whereas its co-migration ability in competition with the wild-type strain was slightly reduced. We conclude that the co-migration of strain BS001 with fungal hyphae through soil is dependent on the presence of functional flagella conferring swimming motility, with the T4P system having a minor effect.

Migration of Paraburkholderia terrae BS001 Along Old Fungal Hyphae in Soil at Various pH Levels

“…Recent work in our lab demonstrated that both systems enhance, but are not essential for, the bacterial migration along with fungal hyphae [4, 5]. In contrast, the presence of functional flagella was found to be essential [4], which was here confirmed and extended to migration against the canonical growth direction of the fungal soil colonizer.…”

“…This was attributed to the fact that the motor proteins, that drive flagellar movement, are powered by the proton motive force [4]. However, in the presence of fungal hyphae in soil, bacterial cells reached the migration sites (forward and backward) generally later at the lower than at the higher pre-set pH values.…”

“…In previous work, the T3SS has been shown to be involved, as a cellular appendix, in the attachment of strain BS001 to fungal hyphae [29], whereas the T4P system has been related to either attachment or twitching motility [4]. Recent work in our lab demonstrated that both systems enhance, but are not essential for, the bacterial migration along with fungal hyphae [4, 5].…”

Climate sensitivity of Cryptomeria japonica in two contrasting environments: Perspectives from QTL mapping

“…This may be a result of the seasonal variation of gas exchange in C. japonica: [47] reported that whole plant evaporation increased significantly from March to April, possibly because this species requires a lot of water for gas exchange (i.e., photosynthesis) during early spring. High water demand during a dry period decreases the plant's water potential; the water deficit further causes dehydration and cavitation in leaf and stem, resulting in cell turgor [48][49][50], which inhibits photosynthesis and metabolic activity [51][52][53]. The response of C. japonica stem growth to water deficit was investigated previously using irrigation experiments [54,55].…”

Fungal hyphae colonization byBacillus subtilisrelies on biofilm matrix components

“…1A). The importance of bacterial flagella and type 4 pili was previously described during co-migration of Burkholderia terrae with fungal hyphae through soil [24], suggesting that essentiality of bacterial motility for fungal interaction could depend on the environment, bacterial physiology or specific properties of the fungal and bacterial cell surfaces. In addition, other examples highlight that fungal hyphae could facilitate bacterial swimming along the hyphae and therefore niche colonization [25,26].…”