Nanotubes Formation in P. aeruginosa

Abstract

The present study discusses a biofilm-positive P. aeruginosa isolate that survives at pH levels ranging from 4.0 to 9.0. The biofilm consortia were colonized with different phenotypes i.e., planktonic, slow-growing and metabolically inactive small colony variants (SCVs). The lower base of the consortia was occupied by SCVs. These cells were strongly attached to solid surfaces and interconnected through a network of nanotubes. Nanotubes were observed at the stationary phase of biofilm indwellers and were more prominent after applying weight to the consortia. The scanning electron micrographs indicated that the nanotubes are polar appendages with intraspecies connectivity. The micrographs indicated variations in physical dimensions (length, width, and height) and a considerable reduction in volume due to weight pressure. A total of 35 cells were randomly selected. The mean volume of cells before the application of weight was 0.288µm3, which was reduced to 0.144 µm3 after the application of weight. It was observed that a single cell may produce as many as six nanotubes, connected simultaneously to six neighbouring cells in different directions. The in-depth analysis confirmed that these structures were the intra-species connecting tools as no free nanotubes were found. Furthermore, after the application of weight, cells incapable of producing nanotubes were wiped out and the surface was covered by nanotube producers. This suggests that the nanotubes give a selective advantage to the cells to resist harsh environmental conditions and weight pressure. After the removal of weight and proper supply of nutrients, these phenotypes reverted to normal planktonic lifestyles. It is concluded that the nanotubes are not merely the phenomenon of dying cells; rather they are a connectivity tool which helps connected cells to tolerate and resist environmental stress.

The Role of Nanotubes in Modulating Colony Spreading and Autolysis in Staphylococcus aureus Biofilms

“…Nanotubes formation in S. aureus was observed. These thin membranous connections between bacterial cells are facilitating intercellular communication and resource exchange within the bio lm community (Ahmed et al, 2022;Pospíšil et al, 2020). Nanotube formation in S. aureus has previously been reported by (Wang, Ko , English, & .…”

“…Bio lm Formation: S. aureus bio lms were developed using the previously described protocol (Ahmed et al, 2022). Brie y, S. aureus isolates were cultured in Tryptic Soy Broth (TSB) for 18 to 24 hours at 35°C.…”

“…These structures were previously reported to be nanotubes involved in the exchange of intracellular material with in the connected cells (Joshi, Gunawan, & Mann, 2021; Singh, Singh, Li, Song, & Singh, 2020). Nanotube formation has recently been reported in multiple bacterial species involved in bio lm formation (Ahmed et al, 2022;Mi, Shi, Wang, & Webster, 2018). Recent data suggest that the nanotube formation may favor bio lm development by enhancing cellular interaction.…”

“…The outer membrane in Gram-negative bacteria has been shown to contribute to nanotube formation by providing structural support and facilitating the exchange of molecules between cells (Baidya, Bhattacharya, Dubey, Mamou, & Ben-Yehuda, 2018; Santos, Figueiredo, Azevedo, Braeckmans, & De Smedt, 2018). However, in Gram-positive bacteria like S. aureus, which lack an outer membrane, the mechanisms driving nanotube formation remain unclear (Ahmed et al, 2022;Pospíšil et al, 2020). Colony spreading is another important characteristic of bacterial bio lms, as it enables the colonization of new areas and the establishment of robust bio lm communities (Guilhen, Forestier, & Balestrino, 2017;Martin, Hölscher, Dragoš, Cooper, & Kovács, 2016).…”

“…Colony spreading is another important characteristic of bacterial bio lms, as it enables the colonization of new areas and the establishment of robust bio lm communities (Guilhen, Forestier, & Balestrino, 2017;Martin, Hölscher, Dragoš, Cooper, & Kovács, 2016). The relationship between nanotube formation and colony spreading in S. aureus bio lms has not been thoroughly investigated (Ahmed et al, 2022;Lin et al, 2016;Pospíšil et al, 2020). It is hypothesized that the presence of nanotubes may affect the ability of S. aureus cells to spread and colonize new surfaces by altering cell-cell interactions and mobility within the bio lm.…”