The development of microbiology has brought many discoveries in recent decades. And one of them is the peculiarities of the movement of flagellated bacteria. The design of the engines of these ancient organisms turned out to be very complex and, according to the principle of their work, is very different from the flagella of our closest eukaryotic relatives of the protozoa. The engine of the flagellate bacterium has been the hottest controversy between creationists and evolutionists. About bacteria, their flagellar motors and much more - this article.
General biology
To begin with, let's remember what kind of organisms they are and what place they occupy in the system of the organic world on our planet. The Bacteria domain unites a huge number of unicellular prokaryotic (without a formed nucleus) organisms.
These living cells appeared on the scene of life almost 4 billion years ago and were the first settlers of the planet. They arecan be of various shapes (cocci, rods, vibrios, spirochetes), but most of them are flagellated.
Where do bacteria live? Everywhere. There are more than 5×1030 on the planet. There are about 40 million of them in 1 gram of soil, up to 39 trillion live in our body. They can be found at the bottom of the Mariana Trench, in hot "black smokers" at the bottom of the oceans, in the ice of Antarctica, and you currently have up to 10 million bacteria on your hands.
The value is undeniable
Despite their microscopic size (0.5-5 microns), their total biomass on Earth is greater than the biomass of animals and plants combined. Their role in the circulation of substances is irreplaceable, and their properties of consumers (destroyers of organic matter) do not allow the planet to be covered with mountains of corpses.
And don't forget about pathogens: plague, smallpox, syphilis, tuberculosis and many other infectious diseases are also caused by bacteria.
Bacteria have found application in human economic activity. Starting from the food industry (sour-milk products, cheeses, pickled vegetables, alcoholic beverages), the green economy (biofuels and biogas) to cell engineering methods and the production of drugs (vaccines, serums, hormones, vitamins).
General morphology
As already mentioned, these unicellular representatives of life do not have a nucleus, their hereditary material (DNA molecules in the form of a ring) are located in a certain area of the cytoplasm (nucleoid). Their cell has a plasma membrane anda dense capsule formed by the peptidoglycan murein. Of the cell organelles, bacteria have mitochondria, there may be chloroplasts and other structures with various functions.
Most bacteria are flagella. The tight capsule on the surface of the cell prevents them from moving around by changing the cell itself, as amoeba do. Their flagella are dense protein formations of various lengths and a diameter of about 20 nm. Some bacteria have a single flagellum (monotrichous), while others have two (amphitrichous). Sometimes flagella are arranged in bundles (lophotrichous) or cover the entire surface of the cell (peritrichous).
Many of them live as single cells, but some form clusters (pairs, chains, filaments, hyphae).
Movement Features
Flagellar bacteria can move in different ways. Some move only forward, and change direction by tumbling. Some are capable of twitching, while others move by sliding.
Bacterial flagella function not only as a cellular "oar", but can also be a "boarding" tool.
Until recently, it was believed that the flagellum of a bacterium wags like a snake's tail. Recent studies have shown that the flagellum of bacteria is much more complicated. It works like a turbine. Attached to the drive, it rotates in one direction. The drive, or flagellar motor of bacteria, is a complex molecular structure that works like a muscle. With the difference that the muscle must relax after contraction, and the bacterial motor works constantly.
Nanomechanism of the flagellum
Without delving into the biochemistry of movement, we note that up to 240 proteins are involved in the creation of the flagellum drive, which are divided into 50 molecular components with a specific function in the system.
In this propulsion system of bacteria, there is a rotor that moves and a stator that provides this movement. There is a drive shaft, bushing, clutch, brakes and accelerators
This miniature engine allows a bacterium to travel 35 times its own size in just 1 second. At the same time, the work of the flagellum itself, which makes 60 thousand revolutions per minute, the body spends only 0.1% of all the energy that the cell consumes.
It is also surprising that the bacterium can replace and repair all the parts of its propulsion mechanism "on the go". Just imagine that you are on an airplane. And technicians change the blades of a running motor.
Flagella vs Darwin
An engine capable of running at speeds up to 60,000 rpm, self-starting and using only carbohydrates (sugar) as fuel, having a device akin to an electric motor - could such a device have evolved?
This is the question Michael Behe, PhD, asked himself in 1988. He introduced into biology the concept of an irreducible system - a system in which all its parts are simultaneously necessary to ensure its operation, and the removal of evenone part leads to a complete disruption of its functioning.
From the standpoint of Darwin's evolution, all structural changes in the body occur gradually and only successful ones are selected by natural selection.
M. Behe's conclusions, set out in the book "Darwin's Black Box" (1996): the engine of a flagellated bacterium is an indivisible system of more than 40 parts, and the absence of at least one will lead to a complete non-functionality of the system, which means that this system is not could have come about through natural selection.
Balm for Creationists
The theory of creation as presented by the scientist and professor of biology, dean of the Faculty of Biological Sciences at the Lehigh University of Bethlehem (USA) M. Behe immediately attracted the attention of church ministers and supporters of the theory of the divine origin of life.
In 2005, Behe even witnessed a lawsuit in the United States, where Behe was a witness from the supporters of the theory of "intelligent design", which considered the introduction of the study of creationism in the schools of Dover in the course "On pandas and people." The process was lost, the teaching of such a subject was recognized as contrary to the current constitution.
But the debate between creationists and evolutionists continues today.
