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Colony Morphology
In microbiology, colonial morphology refers to the visual appearance of bacterial or fungal colonies on an agar plate. Examining colonial morphology is the first step in the identification of an unknown microbe. The systematic assessment of the colonies' appearance, focusing on aspects like size, shape, colour, opacity, and consistency, provides clues to the identity of the organism, allowing microbiologists to select appropriate tests to provide a definitive identification. Procedure When a specimen arrives in the microbiology laboratory, it is inoculated into an agar plate and placed in an incubator to encourage microbial growth. Because the appearance of microbial colonies changes as they grow, colonial morphology is examined at a specific time after the plate is inoculated. Usually, the plate is read at 18–24 hours post-inoculation, but times may differ for slower-growing organisms like fungi. The microbiologist examines the appearance of the colony, noting specific feature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomonas Aeruginosa On Blood Agar
''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of Metabolism, metabolic diversity and consequently are able to colonize a wide range of niches. Their ease of culture ''in vitro'' and availability of an increasing number of ''Pseudomonas'' strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include ''Pseudomonas aeruginosa, P. aeruginosa'' in its role as an opportunistic human pathogen, the plant pathogen ''Pseudomonas syringae, P. syringae'', the soil bacterium ''Pseudomonas putida, P. putida'', and the plant growth-promoting ''Pseudomonas fluorescens, P. fluorescens, Pseudomonas lini, P. lini, Pseudomonas migulae, P. migulae'', and ''P. graminis''. Because of their widespread occurrence in water and plant seeds such as dicots, the pseudomonadaceae, pseudomonads were observed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemolysis (microbiology)
Hemolysis (from Greek αιμόλυση, meaning 'blood breakdown') is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is a ''hemolysin''. Types Alpha-hemolysis When alpha-hemolysis (α-hemolysis) is present, the agar under the colony is light and greenish. ''Streptococcus pneumoniae'' and a group of oral streptococci ( ''Streptococcus'' viridans or viridans streptococci) display alpha hemolysis. This is sometimes called ''green hemolysis'' because of the color change in the agar. Other synonymous terms are ''incomplete hemolysis'' and ''partial hemolysis''. Alpha hemolysis is caused by hydrogen peroxide produced by the bacterium, oxidizing hemoglobin producing the green oxidized derivative methemoglobin. Beta-hemolysis Beta-hemolysis (β-hemolysis), sometimes called ''comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streptococcus Pneumoniae
''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They are usually found in pairs (diplococci) and do not form spores and are non motile. As a significant human pathogenic bacterium ''S. pneumoniae'' was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies. ''Streptococcus pneumoniae'' resides asymptomatically in healthy carriers typically colonizing the respiratory tract, sinuses, and nasal cavity. However, in susceptible individuals with weaker immune systems, such as the elderly and young children, the bacterium may become pathogenic and spread to other locations to cause disease. It spreads by direct person-to-person contact via respiratory droplets and by auto inoculation in persons carrying the bacteria in their upper res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Streptococcus Pyogenes
''Streptococcus pyogenes'' is a species of Gram-positive, aerotolerant bacteria in the genus ''Streptococcus''. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause Group A streptococcal infection. ''S. pyogenes'' is the predominant species harboring the Lancefield group A antigen, and is often called group A ''Streptococcus'' (GAS). However, both '' Streptococcus dysgalactiae'' and the '' Streptococcus anginosus'' group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) ''Streptococcus'' (GABHS) is thus also used. The species name is derived from Greek words meaning 'a chain' () of berries ( a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteus (bacterium)
''Proteus'' is a genus of Gram-negative bacteria. ''Proteus'' bacilli are widely distributed in nature as saprophytes, being found in decomposing animal matter, sewage, manure soil, the mammalian intestine, and human and animal feces. They are opportunistic pathogens, commonly responsible for urinary and septic infections, often nosocomial. The term Proteus signifies changeability of form, as personified in the Homeric poems in Proteus, "the old man of the sea", who tends the sealflocks of Poseidon and has the gift of endless transformation. The first use of the term “Proteus” in bacteriological nomenclature was made by Hauser (1885), who described under this term three types of organisms which he isolated from putrefied meat. Clinical significance Three species—'' P. vulgaris'', '' P. mirabilis'', and '' P. penneri''—are opportunistic human pathogens. ''Proteus'' includes pathogens responsible for many human urinary tract infections. ''P. mirabilis'' causes w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swarming Motility
Swarming motility is a rapid (2–10 μm/s) 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''. This multicellular behavior has been mostly observed in controlled laboratory conditions and relies on two critical elements: 1) the nutrient composition and 2) viscosity of culture medium (i.e. % agar). One particular feature of this type of motility is the formation of dendritic fractal-like patterns formed by migrating swarms moving away from an initial location. Although the majority of species can produce tendrils when swarming, some species like ''Proteus mirabilis'' do form concentric circles motif instead of dendritic patterns. Biosurfactan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prodigiosin
Prodigiosin is the red dyestuff produced by many strains of the bacterium ''Serratia marcescens'', as well as other Gram-negative, gamma proteobacteria such as ''Vibrio psychroerythrus'' and ''Hahella chejuensis''. It is responsible for the pink tint occasionally found in grime that accumulates on porcelain surfaces such as bathtubs, sinks, and toilet bowls. It is in the prodiginines family of compounds which are produced in some Gram-negative gamma proteobacteria, as well as select Gram-positive Actinobacteria (e.g. ''Streptomyces coelicolor''). The name ''prodigiosin'' is derived from ''wikt:prodigious, prodigious'' (''i.e.'' something marvelous). Secondary metabolite Prodigiosin is a secondary metabolite of ''Serratia marcescens''. Because it is easy to detect, it has been used as a model system to study secondary metabolism. Prodigiosin production has long been known to be enhanced by phosphate limitation. In low phosphate conditions, pigmented strains have been shown to g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serratia Marcescens
''Serratia marcescens'' () is a species of rod-shaped, Gram-negative bacteria in the family Yersiniaceae. It is a facultative anaerobe and an opportunistic pathogen in humans. It was discovered in 1819 by Bartolomeo Bizio in Padua, Italy.Serratia marcescens. (2011, April). Retrieved from https://microbewiki.kenyon.edu/index.php/Serratia_marcescens ''S. marcescens'' is commonly involved in hospital-acquired infections (HAIs), also called nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections, and wound infections, and is responsible for 1.4% of HAI cases in the United States. It is commonly found in the respiratory and urinary tracts of hospitalized adults and in the gastrointestinal systems of children. Due to its abundant presence in the environment, and its preference for damp conditions, ''S. marcescens'' is commonly found growing in bathrooms (especially on tile grout, shower corners, toilet water lines, and basins), where it manife ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyoverdin
Pyoverdines (alternatively, and less commonly, spelled as pyoverdins) are fluorescent siderophores produced by certain pseudomonads. Pyoverdines are important virulence factors, and are required for pathogenesis in many biological models of infection. Their contributions to bacterial pathogenesis include providing a crucial nutrient (i.e., iron), regulation of other virulence factors (including exotoxin A and the protease PrpL), supporting the formation of biofilms, and are increasingly recognized for having toxicity themselves. Pyoverdines have also been investigated as "Trojan Horse" molecules for the delivery of antimicrobials to otherwise resistant bacterial strains, as chelators that can be used for bioremediation of heavy metals, and as fluorescent reporters used to assay for the presence of iron and potentially other metals. Due to their bridging the gaps between pathogenicity, iron metabolism, and fluorescence, pyoverdines have piqued the curiosity of scientists around ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyocyanin
Pyocyanin (PCN−) is one of the many toxic compounds produced and secreted by the Gram negative bacterium ''Pseudomonas aeruginosa''. Pyocyanin is a blue secondary metabolite, turning red below pH 4.9, with the ability to oxidise and reduce other molecules and therefore kill microbes competing against ''P. aeruginosa'' as well as mammalian cells of the lungs which ''P. aeruginosa'' has infected during cystic fibrosis. Since pyocyanin is a zwitterion at blood pH, it is easily able to cross the cell membrane. There are three different states in which pyocyanin can exist: oxidized (blue), monovalently reduced (colourless) or divalently reduced (red). Mitochondria play an important role in the cycling of pyocyanin between its redox states. Due to its redox-active properties, pyocyanin generates reactive oxygen species. Biosynthesis Pyocyanin biosynthesis begins with the synthesis of the phenazine-1-carboxylic acid (PCA) core. In this reaction the enzyme PhzE catalyzes the loss of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteus Mirabilis
''Proteus mirabilis'' is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. ''P. mirabilis'' causes 90% of all ''Proteus'' infections in humans. It is widely distributed in soil and water. ''Proteus mirabilis'' can migrate across the surface of solid media or devices using a type of cooperative group motility called swarming. ''Proteus mirabilis'' is most frequently associated with infections of the urinary tract, especially in complicated or catheter-associated urinary tract infections. Diagnosis An alkaline urine sample is a possible sign of ''P. mirabilis''. It can be diagnosed in the lab due to characteristic swarming motility, and inability to metabolize lactose (on a MacConkey agar plate, for example). Also ''P. mirabilis'' produces a very distinct fishy odor. Disease This rod-shaped bacterium has the ability to produce high levels of urease, which hydrolyzes urea to ammonia (NH3), so makes the urine more a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staphylococcus Aureus
''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow without the need for oxygen. Although ''S. aureus'' usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. ''S. aureus'' is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, such as methicillin-resistant ''S. aureus'' (MRSA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
