Living in a Foster Home: The Single Subpolar Flagellum Fla1 of Rhodobacter sphaeroides

Abstract

Rhodobacter sphaeroides is an α-proteobacterium that has the particularity of having two functional flagellar systems used for swimming. Under the growth conditions commonly used in the laboratory, a single subpolar flagellum that traverses the cell membrane, is assembled on the surface. This flagellum has been named Fla1. Phylogenetic analyses have suggested that this flagellar genetic system was acquired from an ancient γ-proteobacterium. It has been shown that this flagellum has components homologous to those present in other γ-proteobacteria such as the H-ring characteristic of the Vibrio species. Other features of this flagellum such as a straight hook, and a prominent HAP region have been studied and the molecular basis underlying these features has been revealed. It has also been shown that FliL, and the protein MotF, mainly found in several species of the family Rhodobacteraceae, contribute to remodel the amphipathic region of MotB, known as the plug, in order to allow flagellar rotation. In the absence of the plug region of MotB, FliL and MotF are dispensable. In this review we have covered the most relevant aspects of the Fla1 flagellum of this remarkable photosynthetic bacterium.

Twists and turns: 40 years of investigating how and why bacteria swim

“…The regulon that looks closest to other alpha proteobacterial flagellar regulons is not expressed under normal laboratory conditions, but the Dreyfus group found that when induced it results in a polar tuft of flagella () [32]. The single, random, swim-stop flagellum we see normally in the lab appears to be the result of horizontal gene transfer [33–35]. It has not been possible to express the two systems together and the conditions causing switching between the two has not been identified.…”

Swimming Using a Unidirectionally Rotating, Single Stopping Flagellum in the Alpha Proteobacterium Rhodobacter sphaeroides

“…While electron micrographs of the isolated motors look similar to the basic motors of enteric species, the Dreyfus laboratory has identified additional motor proteins, an H-ring plus FliL and MotF. These appear to sit in the periplasmic region of the motor close to the outer membrane L/P ring, but unlike related FliL proteins, they appears to interact with the stator and be essential for motility ( Figure 2C ; Suaste-Olmos et al, 2010 ; Ramirez-Cabrera et al, 2012 ; Camarena and Dreyfus, 2020 ). The basic flagellar motors of species such as E. coli have a series of rings in the cytoplasmic and outer membrane.…”

Recent Advances in the Bacterial Flagellar Motor Study

“…All review articles provide both expert and non-expert readers with advances in understanding the structures and functions of the bacterial flagellum. They highlight the most recent observations and illustrate perspectives for future research [4][5][6][7][8][9][10][11][12][13].…”

“…The scope of this Special Issue is to cover recent advances in our understanding of the structures and functions of the bacterial flagellar motor derived from different bacterial species. This Special Issue includes ten review articles [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ] and eleven original research papers [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ] from well-known experts in the field.…”