The Cragie tube or Craigie tube is a method used in microbiology [1] [2] for determining bacterial motility.
Microbiology is the study of microorganisms, those being unicellular, multicellular, or acellular. Microbiology encompasses numerous sub-disciplines including virology, parasitology, mycology and bacteriology.
A hollow tube with some culture medium is placed in semi-solid agar inside a bottle. A sample of the bacterium to be tested is inoculated into the medium in the hollow tube and the setup is incubated at 37 °C overnight.
Agar or agar-agar is a jelly-like substance, obtained from red algae.
On examining the areas where bacterial growth has occurred there are several observations to be made:
Non-motile bacteria are those bacterial species that lack the ability and structures that would allow them to propel themselves, under their own power, through their environment. When non-motile bacteria are cultured in a stab tube, they only grow along the stab line. If the bacteria are mobile, the line will appear diffuse and extend into the medium. The cell structures that provide the ability for locomotion are the cilia and flagella. Coliform and Streptococci are examples of non-motile bacteria as are Klebsiella pneumoniae, and Yersinia pestis. Motility is one characteristic used in the identification of bacteria and evidence of possessing structures: peritrichous flagella, polar flagella and/or a combination of both.
The terms inoculation, vaccination, and immunization are often used synonymously to refer to artificial induction of immunity against various infectious diseases. However, there are some important historical and current differences. In English medicine, inoculation referred only to the practice of variolation until the very early 1800s. When Edward Jenner introduced smallpox vaccine in 1798, this was initially called cowpox inoculation or vaccine inoculation. Soon, to avoid confusion, smallpox inoculation continued to be referred to as variolation and cowpox inoculation was referred to as vaccination. Then, in 1891, Louis Pasteur proposed that the terms vaccine and vaccination should be extended to include the new protective procedures being developed. Immunization refers to the use of all vaccines but also extends to the use of antitoxin, which contains preformed antibody such as to diphtheria or tetanus exotoxins. Inoculation is now more or less synonymous in nontechnical usage with injection and the like, and questions along the lines of "Have you had your flu injection/vaccination/inoculation/immunization?" should not cause confusion. The focus is on what is being given and why, not the literal meaning of the technique used.
Confirmation may be obtained by subculture and retesting.
In biology, a subculture is a new cell or microbiological culture made by transferring some or all cells from a previous culture to fresh growth medium. This action is called subculturing or passaging the cells. Subculture is used to prolong the life and/or expand the number of cells or microorganisms in the culture.
Gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their cell wall.
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagnostic methods used extensively as a research tool in molecular biology.
Coliform bacteria are defined as rod-shaped Gram-negative non-spore forming and motile or non-motile bacteria which can ferment lactose with the production of acid and gas when incubated at 35–37°C. They are a commonly used indicator of sanitary quality of foods and water. Coliforms can be found in the aquatic environment, in soil and on vegetation; they are universally present in large numbers in the feces of warm-blooded animals. While coliforms themselves are not normally causes of serious illness, they are easy to culture, and their presence is used to indicate that other pathogenic organisms of fecal origin may be present. Such pathogens include disease-causing bacteria, viruses, or protozoa and many multicellular parasites. Coliform procedures are performed in aerobic or anaerobic conditions.
A growth medium or culture medium is a solid, liquid or semi-solid designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells.
Shigella dysenteriae is a species of the rod-shaped bacterial genus Shigella. Shigella species can cause shigellosis. Shigellae are Gram-negative, non-spore-forming, facultatively anaerobic, nonmotile bacteria.
The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) or N,N-dimethyl-p-phenylenediamine (DMPD), which is also a redox indicator. The reagent is a dark-blue to maroon color when oxidized, and colorless when reduced. Oxidase-positive bacteria possess cytochrome oxidase or indophenol oxidase. These both catalyze the transport of electrons from donor compounds (NADH) to electron acceptors . The test reagent, TMPD dihydrochloride acts as an artificial electron donor for the enzyme oxidase. The oxidized reagent forms the colored compound indophenol blue. The cytochrome system is usually only present in aerobic organisms that are capable of using oxygen as the terminal electron acceptor. The end-product of this metabolism is either water or hydrogen peroxide.
In microbiology, streaking is a technique used to isolate a pure strain from a single species of microorganism, often bacteria. Samples can then be taken from the resulting colonies and a microbiological culture can be grown on a new plate so that the organism can be identified, studied, or tested.
Instruments used specially in microbiology are as follows:
A Chamberland filter, also known as a Pasteur–Chamberland filter, is a porcelain water filter invented by Charles Chamberland in 1884. It is similar to the Berkefeld filter in principle.
McIntosh and Filde's anaerobic jar is an instrument used in the production of an anaerobic environment. This method of anaerobiosis as others is used to culture bacteria which die or fail to grow in presence of oxygen (anaerobes).
Nutrient agar is a general purpose medium supporting growth of a wide range of non-fastidious organisms. It typically contains (mass/volume):
The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy.
Mannitol motility medium is a bacterial growth medium used to detect the ability of bacteria to ferment mannite and produce nitrogen gas; and to indicate the motility of the organism.
Lautropia mirabilis is a Gram-negative, facultatively anaerobic, oxidase- and catalase-positive, motile bacterium of the genus Lautropia and family Burkholderiaceae, isolated from the mouth of children who were infected with human immunodeficiency virus.
Agar dilution is one of two methods used by researchers to determine the Minimum Inhibitory Concentration (MIC) of antibiotics. It is the dilution method most frequently used to test the effectiveness of new antibiotics when a few antibiotics are tested against a large panel of different bacteria.
In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil flora, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology, before those in virology during the 20th century. Methods of microbial isolation have drastically changed over the past 50 years, from a labor perspective with increasing mechanization, and in regard to the technology involved, and hence speed and accuracy.
An inoculation needle is a laboratory equipment used in the field of microbiology to transfer and inoculate living microorganisms. It is one of the most commonly implicated biological laboratory tools and can be disposable or re-usable. A standard reusable inoculation needle is made from nichrome or platinum wire affixed to a metallic handle. A disposable inoculation needle is often made from plastic resin. The base of the needle is dulled, resulting in a blunted end.
Sulphide Indole Motility (SIM) medium is a bacterial growth medium which tests for the ability to reduce sulfates, the ability to produce indoles, and motility. This combination of challenges in one mixture is convenient and commercially available in stab tubes. Inoculated needles are then punctured into the culture and incubated, if the culture becomes cloudy the bacteria were able to infiltrate the media and survive. This method is particularly useful for pathogenic bacteria which are dangerous to handle on wet mount slides
Vibrio aerogenes is a gram-negative organism that is rod-shaped and has a two-sheathed flagella that is found on one side of the cell that makes it motile. When it is grown on polypeptone-yeast (PY) plate medium, the colonies are usually round and flat. It is an organism that is mesophilic which means it likes temperatures that are between 20-45°C. In addition, it is facultatively anaerobic, which means it can survive with or without oxygen. This is a marine bacteria that is most commonly found in temperatures between 30°C and 35°C and pH 6-7. It requires Na+ to grow and this is what makes the marine environment a necessity for this organism. V. aerogenes can ferment glucose and a few other carbohydrates to yield organic acids.
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