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1、agar A polysaccharide found in seaweed and commonly used to prepare solid culture media.AIDS Acquired immunodeficiency syndrome. The complex of signs and symptoms characteristic of the late phase of human immunodeficiency virus （HIV） infection.algae Photosynthetic, plant-like organisms which general

2、ly lack the complex structure of plants; they may be single-celled or multicellular, and inhabit diverse habitats such as marine and freshwater environments, glaciers, and hot springs.Ames test A method for detecting mutagenic and potentially carcinogenic agents based upon the genetic alteration of

3、nutritionally defective bacteria.ammonification Phase of the nitrogen cycle in which ammonia is released from decomposing organic material.anaerobe A microorganism that grows best, or exclusively, in the absence of oxygen.anaerobic respiration Respiration in which the final electron acceptor in the

4、electron transport chain is an inorganic molecule containing sulfate, nitrate, nitrite, carbonate, etc.antagonism Relationship in which microorganisms compete for survival in a common environment by taking actions that inhibit or destroy another organism.antibiotic A chemical substance from one micr

5、oorganism that can inhibit or kill another microbe even in minute amounts.archaea Prokaryotic single-celled organisms of primitive origin that have unusual anatomy, physiology and genetics, and live in harsh habitats; when capitalized （Archaea） the term refers to one of the three domains of living o

6、rganisms as proposed by Woese.arthrospore A fungal spore formed by the septation and fragmentation of hyphae.ascospore A spore formed within a saclike cell （ascus） of Ascomycota following nuclear fusion and meiosis.ascus Special fungal sac in which haploid spores are created.autoclave A sterilizatio

7、n chamber which allows the use of steam under pressure to sterilize materials. The most common temperature/pressure combination for an autoclave is 121and 15 psi.autotroph A microorganism that requires only inorganic nutrients and whose sole source of carbon is carbon dioxide.bacillus Bacterial cell

8、 shape that is cylindrical （longer than it is wide）.back-mutation A mutation which counteracts an earlier mutation, resulting in the restoration of the original DNA sequence.bacteria Category of prokaryotes with peptidoglycan in their cell wails and a single, circular chromosome. This group of small

9、 cells is widely distributed in the earths habitats.Bacteria （plural of bacterium） When capitalized can refer to one of the three domains of living organisms proposed by Woese, containing all non- archaea prokaryotes.bacterial chromosome A circular body in bacteria that contains the primary genetic

10、material. Also called nucleoid.bacteriophage A virus that specifically infects bacteria.bacterium A tiny unicellular prokaryotic organism that usually reproduces by binary fission and usually has a peptidoglycan cell wall, has various shapes, and can be found in virtually any environment.basidiospor

11、e A sexual spore that arises from a basidium. Found in basidiomycota fungi.bdellovibrio A bacterium that preys on certain other bacteria. It bores a hole into a specific host and inserts itself between the protoplast and the cell wall. There it elongates before subdividing into several cells and dev

12、ouring the host cell.capsule In bacteria, the loose, gel-like covering or slime made chiefly of simple polysaccharides. This layer is protective and can be associated with virulence.Chemoautotroph An organism that relies upon inorganic chemicals for its energy and carbon dioxide for its carbon. Also

13、 called a chemolithotroph.chemoheterotroph Microorganisms that derive their nutritional needs from organic compounds.chemotaxis The tendency of organisms to move in response to a chemical gradient （toward an attractant or to avoid adverse stimuli）.chitin A polysaccharide similar to cellulose in chem

14、ical structure. This polymer makes up the horny substance of the exoskeletons of arthropods and certain fungi.chromosome The tightly coiled bodies in cells that are the primary sites of genes.clone A colony of cells （or group of organisms） derived from a single cell （or single organism） by asexual r

15、eproduction. All units share identical characteristics. Also used as a verb to refer to the process of producing a genetically identical population of cells or genes.colony A macroscopic cluster of cells appearing on a solid medium, each arising from the multiplication of a single mensalism An unequ

16、al relationship in which one species derives benefit without harming the other.conjugation In bacteria, the contact between donor and recipient cells associated with the transfer of genetic material such as plasmids. Can involve special （sex） pili. Also a form of sexual recombination in ciliated pro

17、tozoans.death phase End of the cell growth due to lack of nutrition, depletion of environment, and accumulation of wastes. Population of cells begins to die.decomposition The breakdown of dead matter and wastes into simple compounds, that can be directed back into the natural cycle of living things.

18、diffusion The dispersal of molecules, ions, or microscopic particles propelled down a concentration gradient by spontaneous random motion to achieve a uniform distribution.diploid Somatic cells having twice the basic chromosome number. One set in the pair is derived from the father, and the other fr

19、om the mother.direct, or total cell count 1. Counting total numbers of individual cells being viewed with magnification. 2. Counting isolated colonies of organisms growing on a plate of media as a way to determine population size.endospore A small, dormant, resistant derivative of a bacterial cell t

20、hat germinates under favorable growth conditions into a vegetative cell. The bacterial genera Bacillus and Clostridium are typical sporeformers.eubacteria Term used for non-archaea prokaryotes, stands for true bacteriaeucaryotie cell A cell that differs from a prokaryotic cell chiefly by having a nu

21、clear membrane （a well-defined nucleus）, membrane-bounded subcellular organelles, and mitotic cell division.Eukarya One of the three domains （sometimes called superkingdoms） of living organisms, as proposed by Woese; contains all eukaryotic organisms.eutrophication The process whereby dissolved nutr

22、ients resulting from natural seasonal enrichment or industrial pollution of water cause overgrowth of algae and cyanobacteria to the detriment of fishand other large aquatic inhabitants.fermentation The extraction of energy through anaerobic degradation of substrates into simpler, reduced metabolite

23、s. In large industrial processes, fermentation can mean any use of microbial metabolism to manufacture organic chemicals or other products.fimbria A short, numerous surface appendage on some bacteria that provides adhesion but not locomotion.flagellum A structure that is used to propel the organism

24、through a fluid environment.gene A site on a chromosome that provides information for a certain cell function. A specific segment of DNA that contains the necessary code to make a protein or RNA molecule.generation time Time required for a complete fission cyclefrom parent cell to two new daughter c

25、ells. Also called doubling time.genome The complete set of chromosomes and genes in an organism.genotype The genetic makeup of an organism. The genotype is ultimately responsible for an organisms phenotype, or expressed characteristics.Gram stain A differential stain for bacteria useful in identific

26、ation and taxonomy. Gram-positive organisms appear purple from crystal violet- mordant retention, whereas gram-negative organisms appear red after loss of crystal violet and absorbance of the safranin counterstain.growth curve A graphical representation of the change in population size over time. Th

27、is graph has four periods known as lag phase, exponential or log phase, stationary phase, and death phase.growth factor An organic compound such as a vitamin or amino acid that must be provided in the diet to facilitate growth. An essential nutrient.halophile A microbe whose growth is either stimula

28、ted by salt or requires a high concentration of salt for growth.haploid Having a single set of unpaired chromosomes, such as occurs in gametes and certain microbes.host Organism in which smaller organisms or viruses live, feed, and reproduce.human immunodeficiency virus （HIV） A retro virus that caus

29、es acquired immunodeficiency syndrome （AIDS）.intron The segments on split genes of eucaryotes that do not code for polypeptide. They can have regulatory functions. See exon.in vitro Literally means in glass, signifying a process or reaction occurring in an artificial environment, as in a test tube o

30、r culture medium.in vivo Literally means “in a living being,” signifying a process or reaction occurring in a living thing.Kochs postulates A procedure to establish the specific cause of disease. In all cases of infection: （ 1 ） The agent must be found; （2） inoculations of a pure culture must reprod

31、uce the same disease in animals; （3） the agent must again be present in the experimental animal: and （4） a pure culture must again be obtained.lag phase The early phase of population growth during which no signs of growth occur.L form L-phase variants; wall-less forms of some bacteria that are induced by drugs o