The cell envelope comprises the inner cell membrane and the cell wall of a bacterium. In gram-negative bacteria an outer membrane is included; this envelope is not present in the Mollicutes. Bacterial cell envelopes fall into two major categories: a gram-positive type and a gram-negative type, distinguished by Gram staining. Either type may have an enclosing capsule of polysaccharide for extra protection; as a group these are known as polysaccharide encapsulated bacteria. As in other organisms, the bacterial cell wall provides structural integrity to the cell. In prokaryotes, the primary function of the cell wall is to protect the cell from internal turgor pressure caused by the much higher concentrations of proteins and other molecules inside the cell compared to its external environment; the bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan, located outside of the cytoplasmic membrane. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape.
It is porous and is not considered to be a permeability barrier for small substrates. While all bacterial cell walls contain peptidoglycan, not all cell walls have the same overall structures; this is notably expressed through the classification into gram gram negative bacteria. The gram-positive cell wall is characterised by the presence of a thick peptidoglycan layer, responsible for the retention of the crystal violet dyes during the Gram staining procedure, it is found in organisms belonging to the Actinobacteria and the Firmicutes. Bacteria within the Deinococcus-Thermus group may exhibit gram-positive staining behaviour but contain some cell wall structures typical of gram-negative organisms. Imbedded in the gram-positive cell wall are polyalcohols called teichoic acids, some of which are lipid-linked to form lipoteichoic acids; because lipoteichoic acids are covalently linked to lipids within the cytoplasmic membrane they are responsible for linking the peptidoglycan to the cytoplasmic membrane.
Teichoic acids give the gram-positive cell wall an overall negative charge due to the presence of phosphodiester bonds between teichoic acid monomers. Outside the cell wall, many Gram-positive bacteria have an S-layer of "tiled" proteins; the S-layer assists biofilm formation. Outside the S-layer, there is a capsule of polysaccharides; the capsule helps the bacterium evade host phagocytosis. In laboratory culture, the S-layer and capsule are lost by reductive evolution. Unlike the gram-positive cell wall, the gram-negative cell wall contains a thin peptidoglycan layer adjacent to the cytoplasmic membrane, responsible for the cell wall's inability to retain the crystal violet stain upon decolourisation with ethanol during Gram staining. In addition to the peptidoglycan layer the gram-negative cell wall contains an additional outer membrane composed by phospholipids and lipopolysaccharides which face into the external environment; the charged nature of lipopolysaccharides confer an overall negative charge to the gram -negative cell wall.
The chemical structure of the outer membrane lipopolysaccharides is unique to specific bacterial strains and is responsible for many of the antigenic properties of these strains. As a phospholipid bilayer, the lipid portion of the outer membrane is impermeable to all charged molecules. However, channels called porins are present in the outer membrane that allow for passive transport of many ions and amino acids across the outer membrane; these molecules are therefore present in the periplasm, the region between the plasma membrane and outer membrane. The periplasm contains the peptidoglycan layer and many proteins responsible for substrate binding or hydrolysis and reception of extracellular signals; the periplasm is thought to exist as a gel-like state rather than a liquid due to the high concentration of proteins and peptidoglycan found within it. Because of its location between the cytoplasmic and outer membranes, signals received and substrates bound are available to be transported across the cytoplasmic membrane using transport and signalling proteins imbedded there.
In nature, many uncultivated Gram-negative bacteria have an S-layer and a Capsule. These structures are lost during laboratory cultivation; the Mycobacteria have a cell envelope, not typical of gram-positives or gram-negatives. The mycobacterial cell envelope does not consist of the outer membrane characteristic of gram-negatives, but has a significant peptidoglycan-arabinogalactan-mycolic acid wall structure which provides an external permeability barrier. Therefore, there is thought to be a distinct'pseudoperiplasm' compartment between the cytoplasmic membrane and this outer barrier; the nature of this compartment is not well understood. Acid-fast bacteria, like Mycobacteria, are resistant to decolorization by acids during staining procedures; the high mycolic acid content of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention. The most common staining technique used to identify acid-fast bacteria is the Ziehl-Neelsen stain or acid-fast stain, in which the acid fast bacilli are stained bright red and stand out against a blue background.
The obligate intracellular bacteria in family Chlamydiaceae are unique in their morphology as they do not contain detectable amounts of peptidoglycans. However, the extracellu
Escherichia coli known as E. coli, is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia, found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, are responsible for product recalls due to food contamination. The harmless strains are part of the normal microbiota of the gut, can benefit their hosts by producing vitamin K2, preventing colonization of the intestine with pathogenic bacteria, having a symbiotic relationship. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline afterwards. E. Coli and other facultative anaerobes constitute about 0.1% of gut microbiota, fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. Cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination.
A growing body of research, has examined environmentally persistent E. coli which can survive for extended periods outside a host. The bacterium can be grown and cultured and inexpensively in a laboratory setting, has been intensively investigated for over 60 years. E. coli is a chemoheterotroph whose chemically defined medium must include a source of carbon and energy. E. coli is the most studied prokaryotic model organism, an important species in the fields of biotechnology and microbiology, where it has served as the host organism for the majority of work with recombinant DNA. Under favorable conditions, it takes up to 20 minutes to reproduce. E. coli is a facultative anaerobic and nonsporulating bacterium. Cells are rod-shaped, are about 2.0 μm long and 0.25–1.0 μm in diameter, with a cell volume of 0.6–0.7 μm3. E. Coli stains Gram-negative because its cell wall is composed of a thin peptidoglycan layer and an outer membrane. During the staining process, E. coli picks up the color of the counterstain safranin and stains pink.
The outer membrane surrounding the cell wall provides a barrier to certain antibiotics such that E. coli is not damaged by penicillin. Strains that possess flagella are motile; the flagella have a peritrichous arrangement. It attaches and effaces to the microvilli of the intestines via an adhesion molecule known as intimin. E. coli can live on a wide variety of substrates and uses mixed-acid fermentation in anaerobic conditions, producing lactate, ethanol and carbon dioxide. Since many pathways in mixed-acid fermentation produce hydrogen gas, these pathways require the levels of hydrogen to be low, as is the case when E. coli lives together with hydrogen-consuming organisms, such as methanogens or sulphate-reducing bacteria. Optimum growth of E. coli occurs at 37 °C, but some laboratory strains can multiply at temperatures up to 49 °C. E. coli grows in a variety of defined laboratory media, such as lysogeny broth, or any medium that contains glucose, ammonium phosphate monobasic, sodium chloride, magnesium sulfate, potassium phosphate dibasic, water.
Growth can be driven by aerobic or anaerobic respiration, using a large variety of redox pairs, including the oxidation of pyruvic acid, formic acid and amino acids, the reduction of substrates such as oxygen, fumarate, dimethyl sulfoxide, trimethylamine N-oxide. E. coli is classified as a facultative anaerobe. It uses oxygen when it is available, it can, continue to grow in the absence of oxygen using fermentation or anaerobic respiration. The ability to continue growing in the absence of oxygen is an advantage to bacteria because their survival is increased in environments where water predominates; the bacterial cell cycle is divided into three stages. The B period occurs between the beginning of DNA replication; the C period encompasses the time it takes to replicate the chromosomal DNA. The D period refers to the stage between the conclusion of DNA replication and the end of cell division; the doubling rate of E. coli is higher. However, the length of the C and D periods do not change when the doubling time becomes less than the sum of the C and D periods.
At the fastest growth rates, replication begins before the previous round of replication has completed, resulting in multiple replication forks along the DNA and overlapping cell cycles. E. coli and related bacteria possess the ability to transfer DNA via bacterial conjugation or transduction, which allows genetic material to spread horizontally through an existing population. The process of transduction, which uses the bacterial virus called a bacteriophage, is where the spread of the gene encoding for the Shiga toxin from the Shigella bacteria to E. coli helped produce E. coli O157:H7, the Shiga toxin-producing strain of E. coli. E. coli encompasses an enormous population of bacteria that exhibit a high degree of both genetic and phenotypic diversity. Genome sequencing of a large number of isolates of E. coli and related bacteria shows that a taxonomic reclassification would be desirable. However, this has not been done due to its medical importance, E. coli remains one of the most diverse bacterial species: only 20% of the genes in a typical E. coli genome is shared among all strains.
In fact, from the evolutionary point of view, the members of genus Shigella (S. dysenteriae, S. fle
Teichoic acids are bacterial copolymers of glycerol phosphate or ribitol phosphate and carbohydrates linked via phosphodiester bonds. Teichoic acids are found within the cell wall of most Gram-positive bacteria such as species in the genera Staphylococcus, Bacillus, Clostridium and Listeria, appear to extend to the surface of the peptidoglycan layer, they can be covalently linked to N-acetylmuramic acid or a terminal D-alanine in the tetrapeptide crosslinkage between N-acetylmuramic acid units of the peptidoglycan layer, or they can be anchored in the cytoplasmic membrane with a lipid anchor. Teichoic acids that are anchored to the lipid membrane are referred to as lipoteichoic acids, whereas teichoic acids that are covalently bound to peptidoglycan are referred to as wall teichoic acids; the most common structures are a ManNAcGlcNAc disaccharide with one to three glycerol phosphates attached to the C4 hydroxyl of the ManNAc residue followed by a long chain of glycerol- or ribitol phosphate repeats.
The main function of teichoic acids is to provide rigidity to the cell-wall by attracting cations such as magnesium and sodium. Teichoic acids can be substituted with D-alanine ester residues, or D-glucosamine, giving the molecule zwitterionic properties; these zwitterionic teichoic acids are suspected ligands for toll-like receptors 2 and 4. Teichoic acids assist in regulation of cell growth by limiting the ability of autolysins to break the β bond between the N-acetyl glucosamine and the N-acetylmuramic acid. Lipoteichoic acids may act as receptor molecules for some Gram-positive bacteriophage, it contributes negative charge to the cell wall. Enzymes involved in the biosynthesis of WTAs have been named: TarO, TarA, TarB, TarF, TarK, TarL; this was proposed in 2004. Lipoteichoic acid – a major constituent of the cell wall of gram-positive bacteria Sir James Baddiley
Yersinia pestis is a gram-negative, rod-shaped coccobacillus bacteria, with no spores. It is a facultative anaerobic organism, it causes the disease plague, which takes three main forms: pneumonic and bubonic plagues. All three forms were responsible for a number of high-mortality epidemics throughout human history, including: the sixth century's Plague of Justinian; these plagues originated in China and were transmitted west via trade routes. Recent research indicates that the pathogen may have been the cause of what is described as the Neolithic Decline, when European populations declined significantly; this would push the date to much earlier and might be indicative of an origin in Europe rather than Eurasia. Y. pestis was discovered in 1894 by Alexandre Yersin, a Swiss/French physician and bacteriologist from the Pasteur Institute, during an epidemic of the plague in Hong Kong. Yersin was a member of the Pasteur school of thought. Kitasato Shibasaburō, a German-trained Japanese bacteriologist who practised Koch's methodology, was engaged at the time in finding the causative agent of the plague.
However, Yersin linked plague with Y. pestis. Named Pasteurella pestis in the past, the organism was renamed Yersinia pestis in 1944; every year, thousands of cases of the plague are still reported to the World Health Organization, although with proper treatment, the prognosis for victims is now much better. A five- to six-fold increase in cases occurred in Asia during the time of the Vietnam War due to the disruption of ecosystems and closer proximity between people and animals; the plague is now found in sub-Saharan Africa and Madagascar, areas which now account for over 95% of reported cases. The plague has a detrimental effect on nonhuman mammals. In the United States, mammals such as the black-tailed prairie dog and the endangered black-footed ferret are under threat. Y. pestis is a nonmotile, stick-shaped, facultative anaerobic bacterium with bipolar staining that produces an antiphagocytic slime layer. Similar to other Yersinia species, it tests negative for urease, lactose fermentation, indole.
The closest relative is the gastrointestinal pathogen Yersinia pseudotuberculosis, more distantly Yersinia enterocolitica. The complete genomic sequence is available for two of the three subspecies of Y. pestis: strain KIM, strain CO92. As of 2006, the genomic sequence of a strain of biovar Antiqua has been completed. Similar to the other pathogenic strains, signs exist of loss of function mutations; the chromosome of strain KIM is 4,600,755 base pairs long. Like Y. pseudotuberculosis and Y. enterocolitica, Y. pestis is host to the plasmid pCD1. It hosts two other plasmids, pPCP1 and pMT1 that are not carried by the other Yersinia species. PFra codes for a phospholipase D, important for the ability of Y. pestis to be transmitted by fleas. PPla codes for a protease, that activates plasmin in human hosts and is a important virulence factor for pneumonic plague. Together, these plasmids, a pathogenicity island called HPI, encode several proteins that cause the pathogenesis, for which Y. pestis is famous.
Among other things, these virulence factors are required for bacterial adhesion and injection of proteins into the host cell, invasion of bacteria in the host cell, acquisition and binding of iron harvested from red blood cells. Y. pestis is thought to be descended from Y. pseudotuberculosis, differing only in the presence of specific virulence plasmids. A comprehensive and comparative proteomics analysis of Y. pestis strain KIM was performed in 2006. The analysis focused on the transition to a growth condition mimicking growth in host cells. Numerous bacterial small noncoding RNAs have been identified to play regulatory functions; some can regulate the virulence genes. Some 63 novel putative sRNAs were identified through deep sequencing of the Y. pestis sRNA-ome. Among them was Yersinia-specific Ysr141. Ysr141 sRNA was shown to regulate the synthesis of the type III secretion system effector protein YopJ; the Yop-Ysc T3SS is a critical component of virulence for Yersinia species. Many novel sRNAs were identified from Y. pestis grown in vitro and in the infected lungs of mice suggesting they play role in bacterial physiology or pathogenesis.
Among them sR035 predicted to pair with SD region and transcription initiation site of a thermo-sensitive regulator ymoA, sR084 predicted to pair with fur, ferric uptake regulator. Intergenic RNA thermometer In the urban and sylvatic cycles of Y. pestis, most of the spreading occurs between rodents and fleas. In the sylvatic cycle, the rodent is wild, but in the urban cycle, the rodent is the brown rat. In addition, Y. pestis can spread from the urban environment and back. Transmission to humans is through the bite of infected fleas. If the disease has progressed to the pneumonic form, humans can spread the bacterium to others by coughing and sneezing. Several species of rodents serve as the main reservoir for Y. pes
Lipoteichoic acid is a major constituent of the cell wall of gram-positive bacteria. These organisms external to it, a thick peptidoglycan layer; the structure of LTA varies between the different species of Gram-positive bacteria and may contain long chains of ribitol or glycerol phosphate. LTA is anchored to the cell membrane via a diacylglycerol, it acts as regulator of autolytic wall enzymes. It has antigenic properties being able to stimulate specific immune response. LTA may bind to target cells non-specifically through membrane phospholipids, or to CD14 and to Toll-like receptors. Binding to TLR-2 has shown to induce NF-κB expression, elevating expression of both pro- and anti-apoptotic genes, its activation induces mitogen-activated protein kinases activation along with phosphoinositide 3-kinase activation. LTA's molecular structure has been found to have the strongest hydrophobic bonds of an entire bacteria. Said et al. showed that LTA causes an IL-10-dependent inhibition of CD4 T-cell expansion and function by up-regulating PD-1 levels on monocytes which leads to IL-10 production by monocytes after binding of PD-1 by PD-L.
Department of Oral Biology, Hebrew University-Hadassah Faculty of Dental Medicine, Ein-Kerem Campus, Israel. Lipoteichoic+acid at the US National Library of Medicine Medical Subject Headings
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. A few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, are present in most of its habitats. Bacteria inhabit soil, acidic hot springs, radioactive waste, the deep portions of Earth's crust. Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, only about half of the bacterial phyla have species that can be grown in the laboratory; the study of bacteria is known as a branch of microbiology. There are 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere.
The nutrient cycle includes the decomposition of dead bodies. 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. Data reported by researchers in October 2012 and published in March 2013 suggested that bacteria thrive in the Mariana Trench, with a depth of up to 11 kilometres, is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, "You can find microbes everywhere—they're adaptable to conditions, survive wherever they are."The famous notion that bacterial cells in the human body outnumber human cells by a factor of 10:1 has been debunked. There are 39 trillion bacterial cells in the human microbiota as personified by a "reference" 70 kg male 170 cm tall, whereas there are 30 trillion human cells in the body.
This means that although they do have the upper hand in actual numbers, it is only by 30%, not 900%. The largest number exist in the gut flora, a large number on the skin; the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial in the gut flora. However several species of bacteria are pathogenic and cause infectious diseases, including cholera, anthrax and bubonic plague; the most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and are used in farming, making antibiotic resistance a growing problem. In industry, bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium and other metals in the mining sector, as well as in biotechnology, the manufacture of antibiotics and other chemicals.
Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two different groups of organisms that evolved from an ancient common ancestor; these evolutionary domains are called Archaea. The word bacteria is the plural of the New Latin bacterium, the latinisation of the Greek βακτήριον, the diminutive of βακτηρία, meaning "staff, cane", because the first ones to be discovered were rod-shaped; the ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species.
However, gene sequences can be used to reconstruct the bacterial phylogeny, these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. The most recent common ancestor of bacteria and archaea was a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. Bacteria were involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves related to the Archaea; this involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya. Some eukaryotes that contained mitochondria engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants; this is known as primary endosymbiosis. Bacteria display a wide diversity of sizes, called morphologies.
Bacterial cells are about one-tenth the size of eukaryotic cells
Pseudomonas aeruginosa is a common encapsulated, Gram-negative, 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, its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes. The organism is considered opportunistic insofar as serious infection occurs during existing diseases or conditions – most notably cystic fibrosis and traumatic burns, it affects the immunocompromised but can infect the immunocompetent as in hot tub folliculitis. Treatment of P. aeruginosa infections can be difficult due to its natural resistance to antibiotics. When more advanced antibiotic drug regimens are needed adverse effects may result, it is citrate and oxidase positive. It is found in soil, skin flora, most man-made environments throughout the world.
It thrives not only in normal atmospheres, but in low-oxygen atmospheres, thus has colonized many natural and artificial environments. It uses a wide range of organic material for food; the symptoms of such infections are generalized sepsis. If such colonizations occur in critical body organs, such as the lungs, the urinary tract, kidneys, the results can be fatal; because it thrives on moist surfaces, this bacterium is found on and in medical equipment, including catheters, causing cross-infections in hospitals and clinics. It is able to decompose hydrocarbons and has been used to break down tarballs and oil from oil spills. P. aeruginosa is not virulent in comparison with other major pathogenic bacterial species – for example Staphylococcus aureus and Streptococcus pyogenes – though P. aeruginosa is capable of extensive colonization, can aggregate into enduring biofilms. The word Pseudomonas means "false unit", from the Greek pseudēs and; the stem word mon was used early in the history of microbiology to refer to germs, e.g. kingdom Monera.
The species name aeruginosa is a Latin word meaning verdigris, referring to the blue-green color of laboratory cultures of the species. This blue-green pigment is a combination of two metabolites of P. aeruginosa and pyoverdine, which impart the blue-green characteristic color of cultures. Another assertion is that the word may be derived from the Greek prefix ae- meaning "old or aged", the suffix ruginosa means wrinkled or bumpy; the names pyocyanin and pyoverdine are from the Greek, with pyo-, meaning "pus", meaning "blue", verdine, meaning "green". Pyoverdine in the absence of pyocyanin is a fluorescent-yellow color; the genome of P. aeruginosa consists of a large circular chromosome that carries between 5,500 and 6,000 open reading frames, sometimes plasmids of various sizes depending on the strain. This part of the genome is the P. aeruginosa core genome. P. aeruginosa is a facultative anaerobe, as it is well adapted to proliferate in conditions of partial or total oxygen depletion. This organism can achieve anaerobic growth with nitrite as a terminal electron acceptor.
When oxygen and nitrite are absent, it is able to ferment arginine and pyruvate by substrate-level phosphorylation. Adaptation to microaerobic or anaerobic environments is essential for certain lifestyles of P. aeruginosa, for example, during lung infection in cystic fibrosis and primary ciliary dyskinesia, where thick layers of lung mucus and bacterially-produced alginate surrounding mucoid bacterial cells can limit the diffusion of oxygen. P. aeruginosa growth within the human body can be asymptomatic until the bacteria form a biofilm, which overwhelms the immune system. These biofilms are found in the lungs of people with cystic fibrosis and primary ciliary dyskinesia, can prove fatal. P. aeruginosa relies on iron as a nutrient source to grow. However, iron is not accessible because it is not found in the environment. Iron is found in a insoluble ferric form. Furthermore, excessively high levels of iron can be toxic to P. aeruginosa. To overcome this and regulate proper intake of iron, P. aeruginosa uses siderophores, which are secreted molecules that bind and transport iron.
These iron-siderophore complexes, are not specific. The bacterium that produced the siderophores does not receive the direct benefit of iron intake. Rather, all members of the cellular population are likely to access the iron-siderophore complexes. Members of the cellular population that can efficiently produce these siderophores are referred to as cooperators. Research has shown when cooperators and cheaters are grown together, cooperators have a decrease in fitness, while cheaters have an increase in fitness; the magnitude of change in fitness increases with increasing iron limitation. With an increase in fitness, the cheaters can outcompete the cooperators; these observations suggest that having a mix of cooperators and cheaters can reduce the virulent nature of P. aeruginosa. An opportunistic, nosocomial pathogen of immunocompromised individuals, P. aeruginosa infects the airway, urinary tract and wounds, causes other