Everything Micro

Nitrate Reduction/Nitrate Reductase Test Some bacterial species are able to reduce nitrate (NO3)  to nitrite (NO2)  using the enzyme nitrate reductase in an anaerobic process by using molecules other then oxygen, nitrate, as a terminal electron acceptor.  To determine if a bacteria is able to reduce nitrate they are grown in a nitrate broth and a series of chemical are added to detect nitrate reduction. (A)                                                 (B)                                                     (C)      Nitrate reduction test for the reduction of nitrate in nitrate media, to determine if the bacteria contains nitrate and/or nitrite reductase. Organism were incubated for 48 hr's at 37 degree's in nitrate media then reagents added.  The addition of these reagents test for the presence of nitrites and the media will turn red if nitrites are present. Nitrate broths after the addition of 10 drops reagents A (sulfanilic acid in acetic acid) and B (nn-di

  Streptococcus Identification Identification  of  Streptococcus spp  can cause a range of infections from throat infections, toxic shock an a number of other skin and organ infections that can be  mild to deadly. So it is important to be able to identify and differentitate between the different  Streptococcus spp  for treatment.     After a sample has been isolate and a culture grown a Gram Stain is preformed. Gram stains are the first test performed and  Gram reaction and cell morphology dictates the next test performed.   Streptococcus spp  are Gram (+) and have a rope/chain like appearance.   S. pyogenes (causes Strep throat).  The coccuc/ovoid Gram (+) shaped cells form long distinctive chains ("strepto" greek for twisted chain).  Once the Gram stain is done and Gram (+) coccus are seen then the catalase test is done to differentiate between Staphylococcus and Streptococcus (see blog on S taphlyococcus Identification).  Since Streptlococcus spp

Staphylococcus Identification Identification of Staphylococcus , mainly S. aureus , can cause a range of infections from boils, cellulitus, impetigo, toxic shock and food poisoning.   So it is important to be able to identify and differentitate between the different Staphylococcus spp for treatment.   After a sample has been isolate and a culture grown a Gram Stain is preformed. Gram stains are the first test performed and  Gram reaction and cell morphology dictates the next test performed.  Staphylococcus spp are Gram (+) and have a grape cluster like appearance. Gram stain of Staphylococcus aureus.  Gram (+) (purple colored cells) coccus (round) cell can be seen in cluster arrangements. If the Gram stain is Gram (+) coccus then the next test performed is the Catalase test Organisms that have the catalase enzyme can detoxify the cell of hydrogen peroxide by converting it to oxygen gas. Bubbles indicate oxygen gas production after the addition of hydro