MA Review Chapter 5

Acidophile:

A bacterial organism that grows well in an acid medium.

Mushrooms:

A class of true fungi.

Contagious disease:

A disease that is transmitted from one person to another. The following factors influence the cycle involved in the spread of infectious disease: means of transmission, means of entrance, susceptible host, reservoir host, and means of exit. To prevent infection any part of this cycle must be broken. The cycle of infection begins with the reservoir host.

Mycobacterium:

A genus of bacteria distinguished by a high lipid content that produces resistance to drying, acids, and various germicides. In form, mycobacteria are long, slender, straight or curved rods. Several are highly significant human pathogens that cause tuberculosis, leprosy, granuloma, and skin ulcers.

Staphylococci:

A genus of gram-positive bacteria made up of spherical microorganisms arranged in grapelike clusters.

Streptococci:

A genus of gram-positive bacteria that occurs in chains. They are classified in four types: the pyogenic group, the viridans group, the enterococcus group, and the lactic group.

Chlamydia:

A gram-negative nonmotile obligate intracellular parasite that is totally dependent on the host cell for energy. The genus Chlamydia comprises three species: C. trachomatis, C. psittaci, and C. pneumoniae.

Mycoplasma:

A group of bacteria considered to be the smallest free-living organisms. Unlike most other bacteria, they lack a cell wall. Some are saprophytes, some are parasites, and many are pathogens. They cause primary atypical pneumonia and many secondary infections.

Opportunistic microbe:

A harmless microorganism that causes disease only if it invades the body when the immune system is weakened and unable to defend against it.

Facultative anaerobe:

A microbe that can grow either with or without oxygen but develops most rapidly in an anaerobic environment.

Anaerobe:

A microbe that grows and lives in the absence of oxygen.

Obligate anaerobe:

A microbe that lives only in the absence of oxygen.

Aerobe:

A microorganism that lives and grows in the presence of free oxygen. The majority of microbes are aerobes.

Mycelium:

A network of filaments or strands in mushrooms.

Parasitism:

A one-sided relationship between a host and a parasite.

Commensalism:

A one-sided relationship in which one member benefits and neither is harmed. Yeast, Candida albicans, is one of the normal flora that has a commensal relationship with the skin (meaning that it benefits from contact with the skin but does not harm it).

Obligate intracellular parasite:

A parasite that is completely dependent on its host and must be in a living cell in order to reproduce.

Exotoxin:

A potent toxin that is secreted or excreted by living microorganisms as the result of bacterial metabolism. Exotoxins are the most poisonous substances known to human beings. Bacteria of the genus Clostridium are the most frequent producers of exotoxins.

Photosynthesis:

A process by which the energy of light is used to produce organic molecules. This process is most often used by plants to manufacture carbohydrates, but some bacteria are also capable of photosynthesis.

Opportunism:

A relationship in which a usually harmless organism becomes pathogenic when the host's resistance is impaired.

Mutualism:

A relationship in which both organisms benefit. For example, certain normal flora living in the human intestine synthesize vitamin K, biotin, riboflavin, pantothenate, and pyridoxine.

Gram's stain:

A staining procedure in which bacteria are stained with crystal violet, treated with strong iodine solution, and decolorized with ethanol.

Stain:

A substance used to impart color to tissue or cells in order to study and identify microscopic organisms.

Aflatoxin:

A toxin produced by Aspergillus mold on peanuts and cottonseed. Aflatoxin is extremely toxic to humans and farm animals, and it is also carcinogenic.

Candida albicans:

A type of pathogenic yeast that causes candidiasis. Types of candidiasis include antibiotic candidiasis, candidal vulvovaginitis, diaper candidiasis, oral candidiasis, perianal candidiasis, and systemic candidiasis.

Viron:

A virus that exists outside a host cell.

Bacteriophage or phage:

A virus that has a bacterial host.

Binary fission:

Also called simple fis sion, the common form of asexual reproduction of bacteria in which each bacterium splits into two similar cells.

Enterotoxin:

An exotoxin that affects cells of the intestinal mucosa, causing vomiting and diarrhea.

Microscope:

An instrument used to obtain an enlarged image of a small object and to reveal details of a structure otherwise not distinguishable.

Host:

An organism in which another, usually parasitic, organism is nourished and harbored.

Facultative aerobe:

An organism that is able to grow under anaerobic conditions but grows most rapidly in an aerobic environment.

Parasite:

An organism that lives in, on, or at the expense of another organism without contributing to the host's survival.

Saprophyte:

An organism that obtains its nutrients from dead organic matter. Many bacteria and fungi are saprophytes.

Rickettsia:

Any of several small intracellular parasites of the genus Rickettsia that require a vector (such as fleas, ticks, or lice) to spread disease.

Diplococci:

Any of the spherical or coffee-bean-shaped bacteria that usually appear in pairs.

Characteristics of bacteria:

Bacteria are classified according to morphology, motility, growth, staining reactions, metabolic activities, pathogenicity, antigen-antibody reactions, and genetic composition.

Streptobacilli:

Bacteria in which the rods or filaments tend to fragment into chains. .

Normal (resident) flora:

Bacteria that are permanent and generally beneficial residents in the human body.

Gram-positive bacteria:

Bacteria with cell walls that are composed of peptidoglycan and teichoic acid.

Pathogens:

Disease-causing microorganisms. Only a small percentage of microbes are pathogenic; the others are considered harmless or beneficial.

Fungi:

Eukaryotic organisms with cellulose or chitin cell walls that include mushrooms, molds, and yeasts. Spores, the means of reproduction for fungi, can be carried great distances by the wind and are resistant to heat, cold, acids, bases, and other chemicals.

Microbial growth:

Growth that is dependent on a source of energy and nutrient chemicals and influenced by temperature, pH (acidity), moisture content, and available nutrients. There are three types of microbial metabolism: fermentation, respiration, and photosynthesis.

Viruses:

Infectious agents that are even simpler in nature than bacteria. They are usually not considered cellular. Viruses are composed of a small amount of DNA or RNA wrapped in a protein covering. A virus is visible only with an electron microscope. Viruses are the smallest of all microorganisms

Bacteria:

Microorganisms, the majority of which are harmless. They vary widely in size, shape, and cell arrangement and include bacilli, cocci, spirilla, diplobacilli, streptobacilli, coccobacilli, and cells that appear curved and comma-like.

Molds:

Multicellular fungi that are the main source of antibiotics. Some are used to produce large quantities of enzymes (amylases) and citric acid. Molds can also be harmful, and some are toxic.

Intermediate organisms:

Obligate intracellular parasites, which can reproduce only in living cells. There are three groups: rickettsia, chlamydia, and mycoplasma.

Heterotrophs:

Organisms that obtain carbon from organic material.

Chemotrophs:

Organisms that use chemical substances as a source of energy.

Autotrophs:

Organisms that use inorganic carbon dioxide (CO2) as their basic carbon source.

Phototrophs:

Organisms that use light as a source of energy.

Bacilli:

Rod-shaped bacteria, such as Bacillus anthracis, coliform bacilli, tubercle bacilli, and typhoid bacilli.

Coccobacilli:

Short bacilli that are thick and somewhat ovoid.

Cocci:

Spherical bacteria. Pathogenic cocci are staphylococci, streptococci, and diplococci

Spirilla:

Spiral-shaped bacteria.

Pathogenicity:

The ability of a pathogenic agent to cause a disease.

Dimorphism:

The ability to live in two different forms, such as the few fungi, usually pathogens, that can live either as molds or as yeasts depending on growth conditions.

Legionella pneumophila:

The bacterium that causes Legionnaires' disease. Primarily intracellular, it stains by silver stain.

Virulence:

The degree of pathogenicity or relative power of a microorganism to produce a disease.

Gram's stain limitations:

The following organisms do not Gram's stain well: rickettsia, mycoplasma, treponema, chlamydia, mycobacteria, and Legionella pneumophila

Respiration:

The interchange of gases between an organism and the medium in which it lives.

Optimum pH:

The level of acidity or alkalinity most conducive to functioning. Each microorganism has an optimum pH for growth.

Symbiosis:

The living together of two organisms of different species.

Infective dose:

The number of organisms required to cause a disease in a susceptible host.

Medical microbiology:

The study of pathogens and the disease process, including epidemiology, diagnosis, treatment, infection control, and immunology

Microbiology:

The study of very small living organisms, including bacteria, algae, fungi, protozoa, and viruses; often called microbes, germs, or single-celled organisms.

Nutritional types:

There are two nutritional types of organisms: heterotrophs and autotrophs.

Microorganisms:

Tiny microscopic entities that are able to carry on all the processes of life, including metabolism, reproduction, and motility. Some microorganisms are pathogenic, and others are either beneficial or neutral in relationship to human beings.

Protozoa:

Unicellular eukaryotic organisms of diverse types, once believed to be the lowest forms of animal life. Protozoa have the ability to move, and they are found in water and soil. Protozoa include free-living forms, such as amoebas and paramecia, as well as parasites. Approximately 30 different protozoa are pathogenic to humans. (The singular form is protozoon or protozoan.)

Microorganisms that retain the stain

are said to be gram positive, and those that lose the crystal violet stain by decolorization but stain with a counterstain are said to be gram negative.

There are three basic forms of bacteria:

bacilli, cocci, and spirilla.

There are two main types of microorganisms:

eukaryotes and prokaryotes.