微生物英文名词解释

微生物英文名词解释

1. Mycoplasma：The mycoplasma are a group of the smallest organisms without

cell wall that can be free-living in nature, can pass through bacterial filter and

also grow on laboratory media.

2. Chlamydia：Chlamydia are small Gram-negative bacteria which are obligate

intercellular parasites like virus, but differ from them in that they have both RNA

and DNA, ribosome, cell wall, and divided by binary fission.

3. L forms of bacteria：In osmotically protective media, removal of the bacterial

wall with lysozyme or penicillin liberate protoplasts from Gram-positive cells and

spheroplasts from Gram-negative cells. If such wall-defective cells are able to

grow and divide, they are called L forms. L forms are difficult to cultivate. They

require a special media. Some L form can revert tothe normal bacillary form. L

form in the host may produce chronic infection that are relatively resistant to

antibiotic treatment.

4. Capsule：Many bacteria synthesize large amounts of extracellular polymer when

growing in their natural environments. When the polymer forms a condensed,

well-defined layer closely surrounding the cell, it is called the capsule. With one

known exception (the polypeptide capsule), the polymer is polysaccharide.

5. Pyrogen：This is a fever-producing substance synthesized by bacteria. In fact, it

is the lipopolysaccharide of Gram-negative bacteria. For the injectable

medicament, it is especially important to avoid the contamination of pyrogen in

the course of pharmic production.

6. Exotoxin：Exotoxins are proteins produced inside Gram-positive bacteria cells

and secreted into the environment. These toxins are some of the strongest poisons

known to man and cause violent reactions in host organisms.

7. Endotoxin：Endotoxins are made up of lipids and carbohydrates associated with

the outer membrane of gram-negative bacteria. These toxins usually produce

fever, weakness, and capillary damage.

8. Disinfection: Reduce or eliminate pathogens病原体 in or on inanimate无生命的 objects to a safe level, which are no longer health hazard危险.

9. Sterilization: A physical or chemical process that completely destroys or

removes all microbial life，including bacteria spore and viruses.

10. Antisepsis: Use chemical agents to inhibit or destroy the growth of

microorganisms on skin or other living tissue.

11. Plasmids：Plasmids are small genetic elements that replicate independently of the

bacterial chromosome. Most plasmids are circular, double-stranded DNA

molecules varying from 1,500 to 400,000 base pairs. Like the bacterial

chromosomal DNA, they can autonomously replicate and as such are referred to

as replicons.

12. Transformation：It is the process by which bacteria take up fragments of naked

DNA and incorporate them into their genomes. During transformation, DNA

fragments from a dead degraded bacterium bind to DNA binding proteins on the

surface of a competent recipient bacterium.

13. Conjugation：Conjugation is the transfer of DNA directly from a living donor

bacterium to a recipient bacterium during the mating of the bacteria. A sex pilus

produced by the donor bacterium (or male) binds to the recipient (or female). The

sex pilus then retracts, bringing the two bacteria in contact and the transferred

DNA passes through the sex pilus.

14. Transduction：Transduction is mediated by a bacteriophage, which pick up

fragments of DNA and package them into bacteriophage particles. The DNA is

delivered to infected cells and becomes incorporated into the bacterial genomes.

15. Normal flora: The various bacteria and fungi that are permanent residents of

certain body sites, especially the skin, oropharynx, colon, and vagina.

16. Dysbacteriosis：If flora disequilibrium occurs, for example, when the resident

flora is disturbed, some little significant microorganisms may colonize,

proliferate and produce diseases, which are called dysbacteriosis. Dysbacteriosis

mainly result from long term and large bacteriosis mainly result from long term

and large bacteriosis mainly result from long term and large doses antibiotics

taken. Antibiotics can suppress the drug-susceptible components of fecal flora.

Soon thereafter the counts of fecal flora rise again to normal or higher than

normal levels, principally of organisms selected out because of relative resistance

to the drugs employed. The drug susceptible microorganisms are replaced by

drug-resistant ones and cause correlative disease, microbial selection and

substitution.

17. Toxemia：Bacteria multiply at invading location and do not enter blood stream,

but the exotoxins enter blood and cause corresponding toxic symptoms.

18. Endotoxemia：Gram-negative bacteria multiply at location or in blood stream,

release a lot of amount endotoxin released from bacterial cell rupture.

19. Protein A ：Protein A is a cell wall component of many S. aureus strains that

binds to the Fc portion of IgG molecules except IgG3. The Fab portion of IgG

bound to protein A is free to combine with a specific antigen. Protein A has

become an important reagent in immunology and diagnostic laboratory

technology; for example, protein A with attached IgG molecules directed against

a specific bacterial antigen will agglutinate bacteria that have that antigen

(“coagglutination”). Protein A probably contributes to the virulence of S. aureus

by interfering with opsonization.

20. Elementary body（EB）：Elementary body（EB） are small round cells about

0.2～0.4μm with an electron-dense nucleoid. They possess a cell wall. They are

extracellular form and the environmentally stable infectious particle ，and

metabolically inactive. The EB have a high affinity for host epithelial cells and

rapidly enter them，creating a protected membrane-bound environment around the

chlamydiae，and the Elementary body is reorganized into a larger one called

metabolically active Reticulate body（RB）.

21. Reticulate body（RB）：The intracellular large form known as the reticulate body

Measuring about 0.5～1μm and devoid of an electron-dense nucleoid. Its

presence will reflect the stage of replication. Within the membrane-bound

vacuole，the elementary grows in size and divides into repeatedly by binary

fission. Eventually，the entire vacuole becomes filled with elementary bodies

derived from reticulate bodies to form a cytoplasmic inclusion. The newly formed

elementary bodies may be liberated from the host cell to infect new cells. The

developmental cycle takes 24-48 hours.

22. nucleocapsid ：The simplest of virus particles consists of a protein coat (capsid)

which surrounds a strand of nucleic acid and are thus called naked viruses or

nucleocapsid.

23. Abortive Infections：Not all infections lead to new progeny virus. Productive

infections occur in permissive cells and result in the production of infectious

virus. Abortive infections fail to produce infectious progeny, either because the

cell may be nonpermissive and unable to support the expression of all viral genes

or because the infecting virus may be defective, lacking some functional viral

gene.

24. defective virus ：A defective virus is one that lacks one or more functional genes

required for viral replication. Defective viruses require helper activity from

another virus for some step in replication or maturation. One type of defective

virus lacks a portion of its genome (i.e., deletion mutant). The extent of loss by

deletion may vary from a short base sequence to a large amount of the genome.

Deletion mutants may arise spontaneously or may be constructed in the

laboratory using biochemical techniques.

25. Interferons (IFNs) ：Interferons (IFNs) are proteins made and released by host

cells in response to the presence of pathogens such as viruses, bacteria, parasites

or tumor cells. They allow for communication between cells to trigger the

protective defences of the immune system that eradicate pathogens or tumors.

26. Antigenic drift: Antigenic drift is constantly occurring in both influenza A and

influenza B viruses. The HA and/or NA of the new strain are sufficiently different

to evade (at least partially) the pre-existing human immunity. This leads to the

seasonal epidemics.

27. Antigenic shift: Antigenic shift occurs only in influenza A virus. It describes the

emergence of an entirely new virus sub type. When this new sub type emerges, it

causes a pandemic because there is no pre-existing immunity in humans.