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Mixed culture

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Culture of bacteria where more than one species of bacteria is present.

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Pure Culture

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A bacterial culture with only one species present

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Streak plate

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An agar plate where the bacteria is spread over from another source (culture or environment)

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Quadrant streak

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Each sector is more diluted than the last, one line is dragged from the previous squiggle to make a new squiggle.

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Ubiquitous

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Grows anywhere/isn't hard to grow

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Opportunistic Pathogens

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They are not pathogenic normally but if introduced into a host where the conditions are suitable for growth they could become pathogenic.

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Fastidious

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Picky: the bacteria need their food to be in the form they use internally already in the environment.

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Nonfastidious

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The food they find can be in a different form than they need internally.

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Undefined medium

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The exact components and amounts are unknown eg: beef broth

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Defined medium

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Where all the exact chemical components and amounts are known.

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Aerotolerance

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The oxygen needs of the bacteria.

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Auto-claving tube media

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When this is done the free oxygen in the medium for the most part is removed. When the tube is removed from auto-clave the oxygen is reintroduced but only to the top layers. This forms oxic zones.

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Capnofiles

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Bacteria that survive only when there are high levels of CO2

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Fluid Thioglycollate medium

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Used to grow anaerobic and microaerophilic bacteria. The bacteria is grown in this medium to determine its aerotolerance.

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Cardinal temperatures

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Three points: minimum temp, maximum temp, and finally optimum temp to grow in.

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Psychrophile

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Bacteria that survive only below 20 degrees celcius

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Mesophile

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Bacteria grown between 15 and 45 degrees celcius, ambient temperatures usually and many are pathogens (since they can live in us).

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Thermophile

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Bacteria that need higher temperatures (40-60 degrees celcius) to survive.

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Hyperthermophile

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Bacteria survive only in much higher temperatures of 65-115 degrees celcius.

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Acidophile

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Bacteria that live in pH below 5.5 or highly acidic environments

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Nuetrophile

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Bacteria that live in relatively neutral pH between 5.5 and 8.5

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Alkaliphile

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BActeria that grow in basic environments, above pH 8.5

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Basic stains

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These are alkaline stains that are simple stains normally. They stain the inside of the cell because the alkaline chemical becomes positive and is attracted to the negative cell surface of (most) bacterial cells.

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Chromogen

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The colored molecule of the stain.

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Chromophore

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The component of the chromogen that gives the compound its color, there can be more than one color so more than one chromophore.

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Auxochrome

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The charged portion of the chromogen that will bind chemically to act as a dye.

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Negative stains

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These stains are acidic and so they are negative, this means the chromogen of these stains will repel the bacterial cell surface. The area around the cell is stained as a result.

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Gram Stain

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This is a differential stain that is based on cell wall differences in bacteria. they can be gram positive or negative.

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Gram Positive bacteria

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They appear purple under the gram stain. This is because they resisted decolorization of the primary stain. Their cell wall is made up of multiple layers of peptidoglycan.

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Gram negative bacteria

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These show up as pink in the gram stain because the cell could not resist decolorization of the primary stain. The cell wall is made of two layers (lipid and peptidoglycan) the lipid layers is broken down and the peptidoglycan is porous enough to allow the primary stain to leave the cell.

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Capsule Stain

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The capsule itself can't be stained but the area around it and the cell itself can be. If a space between the two stains appears then the bacteria have capsules.

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Endospore stain

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The endospore resists staining (because of the keratin in it) and so the color must be forced inside, in our case with steam/heat. The mother spore cell is stripped of color and counter-stained differently.

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Central endospore

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The endospore is found in the middle of the mother spore cell.

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Terminal endospore

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The endospore in found at the far side of the mother spore cell. the endospore is just on the edge.

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Subterminal endospre

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The endospore is positioned between the terminal and central locations.

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Manitol Salt Agar

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This is a differential medium that selects for gram positive bacteria. There is a phenol red indicator in the medium that turns yellow in acidic conditions (fermentation) and pink in alkaline. The High NaCl concentration inhibits gram negative bacteria. Staphylococcus bacteria grow on the agar, staphylococcus aureus turns yellow.

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Phenyl ethyl Alcohol Agar

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This inhibits the growth of Gram negative bacteria. This is because the alcohol interferes with DNA synthesis. Gram positive bacteria that will grow on this medium are: staphylococcus, streptococcus, lactococcus, and enterococcus.

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Eosin Methylene Blue Agar

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This will inhibit the growth of gram positive bacteria. Eosin Y and methylene blue are both dyes that inhibit gram positives. This medium indicates for fermenters and coliforms. pink/mucoid=fermentation, little acid, possible coliform. purple/black, maybe metallic green= fermentation, acid production, probable coliform. Colorless=no fermentation, not a coliform.

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Hektoen Enteric Agar

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This is a differential medium that is selective for gram negative bacteria and separates between salmonella and shigella (even proteus). The medium indicates for sulfur reduction (black precipitate where there is H2S gas, because the gas reacts with the iron. Also fermentation, the color changes to either yellow or pink.

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MacConkey Agar

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This is selective for gram negative bacteria, the bile and crystal violet dyes together inhibit all gram positive bacteria. (crystal violet inhibits enterococcus and staphylococcus. Neutral red dye indicates for the presence of acids=turns pink when fermentation occurs. If there is fermentation the bacteria are likely coliforms.

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Phenol red broth

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This is a fermentation test, the substrate can change though. The phenol red indicates for pH, yellow color change= acid production, fermentation. Pink color change=degradation of peptone so alkaline broth. There is an inverted tube inserted to collect any gas.

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Catalase test

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When organisms are aerobic they use oxygen in their electron transport chain as the final electron acceptor. H2O2 is produced and catalase is produced to breakdown this harmful by-product. If the catalase does come into contact with H2O2 then bubbles are formed.

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Citrate Test

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This is a utilization medium where the only source of carbon is sodium citrate, the only source of nitrogen is ammonium phosphate. If the citrate is utilized by the bacteria the bromothymol blue in the agar goes from green to blue bacause the ammonia produced from ammonium phosphate decomposition makes the medium alkaline (ammonium hydroxide is also produced). Only Enterobacteria (gram negative group) will use citrate.

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Starch Hydrolysis test

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The agar has starch as the main nutrient, this is too large of a molecule to enter the cell directly. The bacteria that use it will excrete amylase to break down the starch extracellularly then take in the smaller sugars. Once the bacteria has grown in the agar iodine solution is added. If there is starch the iodine stains it black/brown. Where the bacteria has used the starch there will be a clear area around the growth. This is to separate enterococcus bacteria from other gram positives.

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Casein Hydrolysis test

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This test is to see if the bacteria produce casease to break down casein. If the bacteria has casein then a clearing will show up around the bacteria.

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Casein Hydrolysis test

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This test is to see if the bacteria produce casease to break down casein. If the bacteria has casein then a clearing will show up around the bacteria.

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Sim medium

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This medium conducts many tests at once. The agar is in a tube and the inoculation is done by stabbing the agar. If the bacteria grow anywhere other than the stab line the bacteria are motile. The medium has iron that reacts with H2S gas from sulfur reducing bacteria to form a black precipitate. Kovac's reagent can be added to test for indole (a by-product of tryptophan breaking down through tryptonase action)the medium turns red if there was tryptonase.

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