A pilus is a hair-like cell-surface appendage found on 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.
In biology, quorum sensing or quorum signaling (QS) is the process of cell-to-cell communication that allows bacteria to detect and respond to cell population density by gene regulation, typically as a means of acclimating to environmental disadvantages.
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.
Aliivibrio fischeri is a Gram-negative, rod-shaped bacterium found globally in marine environments. This bacterium grows most effectively in water with a salt concentration at around 20g/L, and at temperatures between 24 and 28°C. This species is non-pathogenic and has bioluminescent properties. It is found predominantly in symbiosis with various marine animals, such as the Hawaiian bobtail squid. It is heterotrophic, oxidase-positive, and motile by means of a tuft of polar flagella. Free-living A. fischeri cells survive on decaying organic matter. The bacterium is a key research organism for examination of microbial bioluminescence, quorum sensing, and bacterial-animal symbiosis. It is named after Bernhard Fischer, a German microbiologist.
Pseudomonas aeruginosa is a common encapsulated, Gram-negative, aerobic–facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, P. aeruginosa is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes. P. aeruginosa is able to selectively inhibit various antibiotics from penetrating its outer membrane - and has high resistance to several antibiotics. According to the World Health Organization P. aeruginosa poses one of the greatest threats to humans in terms of antibiotic resistance.
Microbial intelligence is the intelligence shown by microorganisms. This includes complex adaptive behavior shown by single cells, and altruistic or cooperative behavior in populations of like or unlike cells. It is often 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 the air, 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.
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.
Cyclic di-GMP is a second messenger used in signal transduction in a wide variety of bacteria. Cyclic di-GMP is not known to be used by archaea, and has only been observed in eukaryotes in Dictyostelium. The biological role of cyclic di-GMP was first uncovered when it was identified as an allosteric activator of a cellulose synthase found in Gluconacetobacter xylinus in order to produce microbial cellulose.
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.
Anaeromyxobacter dehalogenans is a species of bacteria. It is an aryl-halorespiring facultative anaerobic myxobacterium. Its cells are slender, gram-negative rods with a bright red pigmentation that exhibit gliding motility and form spore-like structures. The type strain is 2CP-1. Anaeromyxobacter dehalogenans have been found to grow under a minimal amount of electrons acceptors.
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.
Enhygromyxa salina is a species of marine myxobacteria. Like other members of this order, E. salina is a rod-shaped Gram-negative bacterium that can move by gliding and can form aggregates of cells called fruiting bodies. E. salina is slightly halophilic (salt-tolerant) and can grow at lower temperatures than other marine myxobacteria. Several novel secondary metabolites have been identified in the species, including unusual sterols. The species was first described in 2003, based on six strains isolated from samples collected from the coastlines of Japan.
Social motility describes the motile movement of groups of cells that communicate with each other to coordinate movement based on external stimuli. There are multiple varieties of each kingdom that express social motility that provides a unique evolutionary advantages that other species do not possess. This has made them lethal killers such as African trypanosomiasis, or Myxobacteria. These evolutionary advantages have proven to increase survival rate among socially motile bacteria whether it be the ability to evade predators or communication within a swarm to form spores for long term hibernation in times of low nutrients or toxic environments.
Myxococcus llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogochensis is a gram-negative, rod-shaped species of myxobacteria found in soil. It is a predator on other bacteria.
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.
