A pilus is a hair-like appendage found on the surface of many bacteria and archaea. The terms pilus and fimbria can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation. All conjugative pili are primarily composed of pilin – fibrous proteins, which are oligomeric.
A flagellum is a hairlike appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.
The myxobacteria are a group of bacteria that predominantly live in the soil and feed on insoluble organic substances. The myxobacteria have very large genomes relative to other bacteria, e.g. 9–10 million nucleotides except for Anaeromyxobacter and Vulgatibacter. One species of myxobacteria, Minicystis rosea, has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum.
Motility is the ability of an organism to move independently, using metabolic energy.
Microbial intelligence is the intelligence shown by microorganisms. The concept encompasses complex adaptive behavior shown by single cells, and altruistic or cooperative behavior in populations of like or unlike cells mediated by chemical signalling that induces physiological or behavioral changes in cells and influences colony structures.
Myxococcus xanthus is a gram-negative, bacillus species of myxobacteria that is typically found in the top-most layer of soil. These bacteria lack flagella; rather, they use pili for motility. M. xanthus is well-known for its predatory behavior on other microorganisms. These bacteria source carbon from lipids rather than sugars. They exhibit various forms of self-organizing behavior in response to environmental cues. Under normal conditions with abundant food, they exist as predatory, saprophytic single-species biofilm called a swarm, highlighting the importance of intercellular communication for these bacteria. Under starvation conditions, they undergo a multicellular development cycle.
Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in mutualistic, commensal and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations.
Swarming motility is a rapid and coordinated translocation of a bacterial population across solid or semi-solid surfaces, and is an example of bacterial multicellularity and swarm behaviour. Swarming motility was first reported by Jorgen Henrichsen and has been mostly studied in genus Serratia, Salmonella, Aeromonas, Bacillus, Yersinia, Pseudomonas, Proteus, Vibrio and Escherichia.
Bacterial motility is the ability of bacteria to move independently using metabolic energy. Most motility mechanisms that evolved among bacteria also evolved in parallel among the archaea. Most rod-shaped bacteria can move using their own power, which allows colonization of new environments and discovery of new resources for survival. Bacterial movement depends not only on the characteristics of the medium, but also on the use of different appendages to propel. Swarming and swimming movements are both powered by rotating flagella. Whereas swarming is a multicellular 2D movement over a surface and requires the presence of surfactants, swimming is movement of individual cells in liquid environments.
Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis. Phototaxis is called positive if the movement is in the direction of increasing light intensity and negative if the direction is opposite.
Gliding motility is a type of translocation used by microorganisms that is independent of propulsive structures such as flagella, pili, and fimbriae. Gliding allows microorganisms to travel along the surface of low aqueous films. The mechanisms of this motility are only partially known.
Vampirococcus is an informally described genus of ovoid Gram-negative bacteria, but the exact phylogeny remains to be determined. This predatory prokaryote was first described in 1983 by Esteve et al. as small, anaerobic microbe about 0.6 μm wide before being given the name of Vampirococcus in 1986 by Guerrero et al. This prokaryote is a freshwater obligate predator that preys specifically on various species of the photosynthetic purple sulfur bacterium, Chromatium. As an epibiont, Vampirococcus attaches to the cell surface of their prey and "sucks" out the cytoplasm using a specialized cytoplasmic bridge. They are commonly mentioned as an example of epibionts when discussing strategies employed by bacterial predators. This microbe still has yet to be classified based on genomic sequencing or 16S rRNA because it cannot be sustained long enough outside its natural environment to isolate a pure culture.
Pxr sRNA is a regulatory RNA which downregulates genes responsible for the formation of fruiting bodies in Myxococcus xanthus. Fruiting bodies are aggregations of myxobacteria formed when nutrients are scarce, the fruiting bodies permit a small number of the aggregated colony to transform into stress-resistant spores.
Stigmatella aurantiaca is a member of myxobacteria, a group of gram-negative bacteria with a complex developmental life cycle.
Myxococcus is a genus of bacteria in the family Myxococcaceae. Myxococci are Gram-negative, spore-forming, chemoorganotrophic, obligate aerobes. They are elongated rods with rounded or tapered ends, and they are nonflagellated. The cells move by gliding and can predate other bacteria. The genus has been isolated from soil.
Twitching motility is a form of crawling bacterial motility used to move over surfaces. Twitching is mediated by the activity of hair-like filaments called type IV pili which extend from the cell's exterior, bind to surrounding solid substrates, and retract, pulling the cell forwards in a manner similar to the action of a grappling hook. The name twitching motility is derived from the characteristic jerky and irregular motions of individual cells when viewed under the microscope. It has been observed in many bacterial species, but is most well studied in Pseudomonas aeruginosa, Neisseria gonorrhoeae and Myxococcus xanthus. Active movement mediated by the twitching system has been shown to be an important component of the pathogenic mechanisms of several species.
Marine prokaryotes are marine bacteria and marine archaea. They are defined by their habitat as prokaryotes that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. All cellular life forms can be divided into prokaryotes and eukaryotes. Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, whereas prokaryotes are the organisms that do not have a nucleus enclosed within a membrane. The three-domain system of classifying life adds another division: the prokaryotes are divided into two domains of life, the microscopic bacteria and the microscopic archaea, while everything else, the eukaryotes, become the third domain.
Run-and-tumble motion is a movement pattern exhibited by certain bacteria and other microscopic agents. It consists of an alternating sequence of "runs" and "tumbles": during a run, the agent propels itself in a fixed direction, and during a tumble, it remains stationary while it reorients itself in preparation for the next run.
Adventurous motility is as a type of gliding motility; unlike most motility mechanisms, adventurous motility does not involve a flagellum. Gliding motility usually involves swarms of bacteria; however, adventurous motility is practiced by individual cells. This gliding is hypothesized to occur via assembly of a type IV secretion system and the extrusion of a polysaccharide slime, or by use of a series of adhesion complexes. The majority of research on adventurous motility has focused on the species, Myxococcus xanthus. The earliest of this research is attributed to Jonathan Hodgkin and Dale Kaiser.
