Chapter 6 – Microbiology Test Questions – Flashcards
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| Requirements for growth |
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| physical (temperature, pH, osmotic pressure) |
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| Temperature |
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| Each bacterial species has its own particular minimum, optimum, and maximum growth temperatures |
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| minimum |
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| lowest temperature a species will grow at |
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| optimum |
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| temperature the species grows best at |
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| maximum |
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| the highest temperature at which growth for a particular species is possible |
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| Psychrophiles |
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| cold loving microbes can grow at 0c Optimum temperature is high |
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| Mesophiles |
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| moderate temperature loving microbes Optimum growth temperature is 25 to 40c Many pathogenic bacteria have an optimum temperature of about 37c, and are mesophiles |
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| Thermophiles |
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| heat loving microbes endospores are usually heat resistant may survive heat treatment optimum growth temperature is 50 to 60C |
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| Aerobes |
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| Microbes that use molecular oxygen |
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| Anaerobes |
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| Microbes that do not use oxygen |
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| Aerotolerant Anaerobes |
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| do not use oxygen for growth, but they can tolerate it and grow in the presence of oxygen |
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| Microaerophiles |
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| aerobic growth, oxygen is required in concentrations lower than those in air, they are sensitive to superoxide free radicals and peroxides that they produce when in oxygen-rich conditions |
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| Halophilic |
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| describes organisms that can tolerate high salt concentrations |
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| facultative Anaerobes |
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| can use oxygen when it is present, but can still grow without oxygen by using fermentation or anaerobic respiration |
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| Capnophile |
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| A microorganism that grows best at relatively high CO2 concentrations |
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| Identify ways in which aerobes avoid damage by toxic forms of oxygen |
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| Enzymes such as catalase and superoxide dismutase (SOD) neutralize toxic forms of oxygen |
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| DNA |
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| is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life. |
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| RNA |
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| is one of the three major macromolecules (along with DNA and proteins) that are essential for all known forms of life. Like DNA, RNA is made up of a long chain of components called nucleotides. Each nucleotide consists of a nucleobase (sometimes called a nitrogenous base), a ribose sugar, and a phosphate group. The sequence of nucleotides allows RNA to encode genetic information. All cellular organisms use messenger RNA (mRNA) to carry the genetic information that directs the synthesis of proteins. In addition, some viruses use RNA instead of DNA as their genetic material; Like proteins, some RNA molecules play an active role in cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals. One of these active processes is protein synthesis, a universal function whereby mRNA molecules direct the assembly of proteins on ribosomes. This process uses transfer RNA (tRNA) molecules to deliver amino acids to the ribosome, where ribosomal RNA (rRNA) links amino acids together to form proteins. |
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| Protein |
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| A large molecule containing carbon, hydrogen, oxygen, and nitrogen; some proteins have a helical structure and others are pleated sheets |
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| Transformation |
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| The process in which genes are transferred from one bacterium to another as "naked" DNA in solution. The changing of a normal cell into a cancerous cell |
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| Transduction |
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| The transfer of DNA from one cell to another by a bacteriophage |
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| phenotype |
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| The external manifestations of an organism's genotype, or genetic makeup |
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| genotype |
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| The genetic makeup of an organism |
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| mutation |
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| Any change in the nitrogenous base sequence of DNA |
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| conjugation |
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| The transfer of genetic material from one cell to another involving cell-to-cell contact |
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| plasmid |
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| A small circular DNA molecule that replicates independently of the chromosome |
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| Selective Media |
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| suppress the growth of unwanted bacteria and encourage the growth of the desired organisms Example is Sabouraud's dextrose agar. The pH 5.6 is selective for fungi that should outgrow most bacteria at this pH |
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| Differential Media |
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| used to distinguish colonies of the desired organism from other colonies growing on the same plate Example is blood agar--it distinguishes hemolytic colonies from other colonies on the same plate. The blood makes it differential. Streptococcus pyogenes causes strep throat and is hemolytic (lyses red blood cells) |
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| Media that is both Selective and Differential |
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| Mannitol Salt Agar: used to culture Staphyloccus aureus which has a high tolerance for sodium chloride; it can also ferment the carbohydrate mannitol into an acid. The NaCl makes it selective for halophiles because the NaCL discourages the growth of competing organisms while favoring the growth of halophiles such as S. aureus Differential because you can distinguish those colonies that ferment mannitol from those that do not. The reagents that make it differential are the mannitol and pH indicator yellow--mannitol red for non-mannitol |
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| MacConkey Agar |
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| Selective for Gram-negative enteric organisms. Bile salts and crystal violet make it selective because bile salt encourages enteric organisms and crystal violet inhibits the growth of gram-positive bacteria |
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| MacConkey Agar |
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| It is differential because it distinguishes lactose fermenters from non-fermenters. The reagents are lactose and a pH indicator. Colonies that can ferment lactose are red or pink, and can be distinguished from colorless colonies that do not ferment lactose |
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| Enrichment culture |
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| selective sort of increase numbers an enrichment medium is usually liquid and provides nutrients and environmental conditions that favor the growth of a particular micobe, but not others. Similar to selective media, but designed to increase the numbers of desired microbes to detactable levels |
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| Chemically define media |
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| exact chemical composition is known. It is used for the growth of chemoautotrophs and photoautotrophs, and in microbiological assays |
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| Complex defined media |
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| made up of nutrients including the extracts of yeast, meat, or plants, or digests of proteins. Their chemical composition varies slightly from batch to batch. Used for the growth of most chemoheterotrophic organisms |
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| Sterilization |
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| Refers to the destruction of all forms of microbe life, including endospores. The most common method of sterilization is heating (steam under pressure or sterilizing gas) |
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| Commerical Sterilization |
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| Limited heat treatment. because the heat required for absolute sterility of canned food would degrade the quality of food, food is heated enough to destory Clostridium botulinum endospores |
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| Endospore |
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| A resistant, dormant structure formed within a cell that protects a bacterium from adverse environmental conditions |
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| Disinfection |
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| the destruction of vegetative pathogens only |
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| Antiseptic |
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| a chemical that destroys vegetative pathogens on living tissue |
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| degerming |
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| the mechanical removal of microbes from a limited area |
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| sanitizer |
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| used for treatment intended to lower microbial counts on eating and drinking utensils to minimize pathogen transmission from one user to another |
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| Germicide |
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| Kills microrganisms |
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| Bactericidal |
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| Kills bacteria |
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| bacteriostatic |
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| inhibits the growth and multiplication of bacteria, once the bacteriostatic agent is removed, growth can resume |
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| aseptic |
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| an object or area is free of pathogens; aseptic techniques are used to minimize contamination |
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| heat |
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| kills microorganisms by denaturing their enzymes. A disadvantage includes that heat resistance varies with different organisms |
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| thernal death point |
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| lowest temperature that will kill all the microorganisms in a liquid suspension in 10mins |
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| thernal death time |
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| minimum length of time to kill all bacteria in a liquid culture at a give temperature |
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| decimal reduction time |
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| the time, in minutes, it takes to kill 90% of the population of bacteria at a given temperature |
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| moist heat |
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| kills microorganisms primarily by protein denaturation (involving the breakage of hydrogen bonds) |
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| boiling |
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| advantages include that it kills vegetative forms of bacterial pathogens, most viruses, fungi, and their spores within about 10mins disadvantage: endospores and some virsus are not destroyed this quickly not always a reliable method of sterilization used to wash dishes, basins, equipment causes protein denaturation |
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| autoclave |
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| steam under pressure this is the preferred method of sterilization unless the higher temperatures or moisture can damage the material steam must directly contat the material to be sterilized higher the pressure, higher the temperature causes protein denaturation |
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| pasteurization |
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| high-temperature short time HTST a high temperature is used for a short time 72C for 15seconds to destory pathogens without altering the flavor of the food ultra-high-temperature UHT treatment 140C for 3 seconds is used to sterilize dairy products causes protein denaturation |
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| What is meant by equivalent treatments? |
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| As temperature is increased, much less time is needed to kill the same number of microbes. For this reason 63C for 30minutes and 72C for 15seconds could be considered equivalent treatments |
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| dry heat |
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| direct flaming: involves burning contaminations example is sterilizing an inoculationg loop with a Bunsen Burner |
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| incineration |
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| very effective; also involves burning contaminants and can also be used to sterilize inoculating loop |
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| hot-air sterilization |
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| items are put in an oven at about 170c for 2hrs, causes oxidation. Very effective, but requires higher temperatures and longer periods of time than with moist heat. Mechanism of action is oxidation |
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| filtration |
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| involves pouring liquid or gas through a screen with small pores to filter out microorganism advantage is that it can be used to sterilize heat-sensitive materials the mechanism of action is the separation of the organisms from the suspending liquid high-efficiency particulate air HEPA filters remove microorganisms larger than 0.3um in diameter there are filters of different sizes down to about 0.01um |
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| low temperatures |
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| refrigerations 0-7c slows metabolic rate of microorganisms so they do not reporduce or synthesize toxins decreased chemical reactions and changes in proteins |
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| deep freezing |
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| cultures are quick frozen between -50 and -92 the temperature causes the microbes to go dormant with decreased chemical reactions and changes in proteins used for food, drug, and culure preservation |
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| phenol |
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| disrupts plasma membrane denatures enzymes disadvantages include its irritating qualities and odor |
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| phenolics |
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| derivatives of phenol cause disruption of lipid-containing plasma membranes reduced irritating qualities used on environmental surfaces, instruments, skin surfaces, and mucous membrane |
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| bisphenols |
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| derivatives of phenol probably disrupt plasma membrane used as a disinfectant in hand soap and skin lotions |
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| halogens |
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| include iodine and chlorine antimicrobial activity is caused by hypochlorous acid from adding chlorine to water |
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| Man DNA |
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| DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription |
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| Baterica DAN |
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| Most bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular chromosome located in the cytoplasm in an irregularly shaped body called the nucleoid.[63] The nucleoid contains the chromosome with associated proteins and RNA. The order Planctomycetes are an exception to the general absence of internal membranes in bacteria, because they have a double membrane around their nucleoids and contain other membrane-bound cellular structures.[64] Like all living organisms, bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from those of eukaryotes and Archaea.[65] |
