BioScience Dictionary

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Found Gram-negative 22 times.

Displaying results 1 to 10.

1. Acetobacter
Acetobacter is a genus of rod-shaped, flagellated or nonmotile gram-negative bacteria that oxidize ethanol to acetic acid . These bacteria are commonly found on fruits and vegetables, and although they are used commercially to produce vinegar (especially Acetobacter aceti), they're considered pests by brewers and vintners.

2. Agrobacterium tumefaciens
Agrobacterium tumefaciens is a gram-negative bacterium found in soil which causes crown gall disease in plants (which causes tumor s to form at the crown and at the junction of the root and stem). The tumors are caused by the Ti plasmid in the bacterium; this plasmid is being heavily researched by plant genetic engineers because it is a useful way to introduce new genes into a plant cell.

3. Aztobacter (nitrogen-fixing bacteria)
Aztobacter is a species of large, oval, aerobic gram-negative bacteria that can fix atmospheric nitrogen if they have an energy source (often a carbohydrate ) available.

4. Bacteroid
* Resembles a bacterium . * A particular group of small, gram-negative , anaerobic , rod-shaped bacteria. * A cell which was modified from a bacteria that has become an endosymbiont within other organisms, like plants or marine animals.

5. Chlamydia
A genus of gram-negative bacteria which is a parasite living within the cell s of humans and other animals, causing a wide variety of diseases. In humans, they cause inclusion conjunctivitis and the venereal (sexually-transmitted) disease by the same name. This STD causes symptoms such as abnormal genital discharge and pelvic pain (in women), but often it produces no symptoms at all. If left untreated, it can cause pelvic inflammatory disease in women (which can lead to sterility and other problems) and, if transmitted during birth, can cause eye infections and pneumonia in newborns. It can be cured with antibiotics.

6. Coliform
gram-negative , nonsporing, facultative rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 35 degrees C. Examples of coliform bacteria are members in the genera Escherichia ( e.g. E. coli ), Klebsiella (e.g. K. pneumoniae), Enterobacter (e.g. E. cloacai), and Citrobacter (e.g. C. freundii).

7. Coliforms
A group of bacteria which live within the bowels of larger organism s and ferment a sugar called lactose, producing gas within 48 hours of growth. They are generally small, gram-negative , bacilliform (shaped like rods), facultative anaerobe s and they include strains such as Escherichia , Kelbsiella, Enterobacter, and Citrobacter. They are useful for measuring the amount of water pollution by feces.

8. Endotoxin
Any of a group of poisonous lipopolysaccharide s found in the outer membranes of gram-negative bacteria . These toxins cause illnesses such as diarrhea and hemorragic shock.

9. Gram stain
An important method for staining bacteria developed by Christian Gram in 1884. The bacteria are placed as a smear on a slide, then air-dried, then stained first with crystal violet dye and then with Gram's iodine, then washed with 95% ethanol, flooded with safranin or fuchsin (red dyes) and air-dried again. If the bacteria retain the purple-blue stain on their cell walls, they're classified as Gram-positive; if they don't retain the crystal violet but take the red counterstain, they're gram-negative. This classification is important because the reaction to Gram stain correlates in many cases with the bacteria's vulnerability to certain antibiotic s. The process only takes a few minutes, making it ideal for medical clinics. If a clinician considers data from the Gram stain along with his/her medical examination of a sick patient, the clinician can get a pretty good idea of the pathogen that is infecting the patient and then start a regimen of antibiotics. In a clinical setting, the Gram stain is followed up by a bacterial culture (which takes three to six days to complete).

10. Gram-negative
To describe a prokaryotic cell whose cell wall stains pink (negative) in Gram stain . The cell wall of a gram-negative bacterium contains relatively little peptidoglycan but contains an outer membrane composed of lipopolysaccharide (LPS), lipoprotein , and other complex macromolecule s.