21. Different arrangements of bacterial flagella. Flagella movement. Correlation of swimming behavior and flagellar rotation. Taxis

There are basically four different types of flagellar arrangements:

1. A single flagellum can extend from one end of the cell - if so, the bacterium is said to be monotrichous.

2. A single flagellum (or multiple flagella; see below) can extend from both ends of the cell - amphitrichous.

3. Several flagella (tuft) can extend from one end or both ends of the cell - lophotrichous; or,

4. Multiple flagella may be randomly distributed over the entire bacterial cell - peritrichous.

Flagella movement.trictly speaking are the cilia and flagellar movements of eucaryotes intracellular movements; for although a flagellum (or a cilium) seems to be an appendage of the cell, is it surrounded by the plasma membrane. All dynein molecules along the whole length of the microtubule have continuously to be supplied with sufficient amounts of ATP. Both ion milieu and pH of their surrounding has to be right. P. SATIR (1968, 1976 at that time at the University of California, Berkeley) described the process of movement as a sliding filament mechanism where the peripheral tubuline doublets slide past each other. In the course of this contacts the dynein that is always anchored to the A tubule the B tubule of the neighbouring doublet with its tips. This mechanism explains the forward and back strokes of the cilium but not the numerous variations of cilia movements found mainly with protozoa. There exist pulling and pushing flagella, as well as tinsel-type flagella. There exist flagella that rotate around an imaginary axis and flexible flagella where the movement spreads wave-like along the axis. Many motile cells can change into forward or reverse gear or can carry out more or less strong corrections of the course. Cilia differ from flagella only in their number per cell. They are usually quite short and cover often the whole surface of a cell. Cilia are rare in plants, an often cited example are the zoospores of Vaucheria sessilis.. With algae (except red algae) are flagellated stages common. They are often found with the spermatozoids (male germ cells) of mosses and ferns. Early during the evolution of seed plants were flagellated stages more and more driven out. Among the few still existing exceptions are the spermatozoids of Gingko biloba and the cycads. Movements are often controlled by extern signals. Many protists are attracted by certain sources of stimulation called taxis: light (phototactic behaviour) or certain chemicals (chemotactic behaviour). Usually follows the motion a concentration or intensity gradient. If a threshold of sensation is passed, begins a reverse reaction. During the last decades was signal recognition a much-studied topic. We know, for example, that the carotenoids within the stigma of some algae (Euglena, for example) are sensitive to blue light. The chloroplast movements of the alga Mougeotia are controlled by the phytochrome system and germ cells (of algae) react to species specific sexual attractants. But how the perceived signal is converted and how signals of the same or the opposite kind are co-ordinated in a directed movement is not even basically understood (black box). The basis of many flagella is equipped with a complexly structured basal body. M. MELKONIAN (Botanisches Institut der Universität Köln) analyzed the basal bodies of a number of algae and found group-specific patterns. He rated these structures and their variations as traits that help to understand the family relations of the single groups of algae significantly. Correlation of swimming behavior and flagellar rotation. Taxis In molecular biology, the flagellar motor switch is a protein complex. In Escherichia coli and Salmonella typhimurium it regulates the direction offlagellar rotation and hence controls swimming behaviour.The switch is a complex apparatus that responds to signals transduced by thechemotaxis sensory signalling system during chemotactic behaviour. CheY, the chemotaxis response regulator, is believed to act directly on the switch to induce tumbles in the swimming pattern, but no physical interactions of CheY and switch proteins have yet been demonstrated. The switch complex comprises at least three proteins - FliG, FliM and FliN. It has been shown that FliG interacts with FliM, FliM interacts with itself, and FliM interacts with FliN Several amino acids within the middle third of FliG appear to be strongly involved in the FliG-FliM interaction, with residues near the N- or C-termini being less important. Such clustering suggests that FliG-FliM interaction plays a central role in switching. Analysis of the FliG, FliM and FliN sequences shows that none are especially hydrophobic or appear to be integral membrane proteins.^[3] This result is consistent with other evidence suggesting that the proteins may be peripheral to the membrane, possibly mounted on the basal body M ring.FliG is present in about 25 copies per flagellum. The structure of the C-terminal domain of FliG is known, this domain functions specifically in motor rotation.