Unknown Bacteria Sample #15 Lab Report Sanzida Tasli Taslim m
Abstract
The goal of this lab experiment was to identify an unknown bacteria sample using different selective and differential media. The different agar plates were streaked with this unknown bacteria and left to incubate for 24 hours. The results from the the growth of the bacteria on the agar plates show that there was contamination of the plates during some part of the procedure. The carrying results suggested that the unknown bacteria was possibly salmonella, and was contaminated with acid producing B. Meg bacteria. ne plate, the Brilliant !reen "gar, was an outlier from this hypothesis, but picture results suggests that there may have been an error when this plate was being prepared, which caused cau sed it to produce the no growth results. Introduction
The ob#ective of this lab experiment is to identify an unknown bacteria sample using the different agar plates, filled with selective and differential media. $elective media is media that contains certain ingredients or conditions that only allow for the growth of particular physiological types of microbes. %ifferential %ifferential media is media which contains ingredients that allows differentiation between different bacterial types based on the colony morphology or the reactions produced by the bacteria bac teria in the medium. There is medium that can be b e described as both selective and differential. &or example, Mannitol $alt "gar contains '.() salt, which inhibits many non*halophilic organisms. This plate is used as a selective medium for $taphylococci, which can withstand these conditions. +t also contains mannitol, a sugar staphylococci can use to produce fermentation. +ts p indicator is -henol ed, which changes to yellow in the presence of acid, which show lactic acid produced during fermentation, therefore differentiating fermenting bacteria and non* fermenting bacteria. /osin*Methylene Blue agar plate allows differentiation between enteric lactose fermenters and non*fermenters. +t is also used to identify /. 0oli, due to the fact that this bacteria produces a characteristic blue*black color with a metallic green sheen. -ink and mucoid growth, or 1dark
3purple to black growth show possible coliform bacteria formation. -ink growth is ev ident of little acid production and dark shows a lot of acid production. 5ogel 6ohnson agar plates can be considered as both selective and differential medium. +t can detect $. aureus, which is identified the coa gulase*positive and mannitol*fermenting strains. +t contains tellurite, lithium chloride, and high glycine concentration for inhibition of organisms. +t can also detect staphylococci carriers. ektoen "gar -lates can also be considered a differential and selective media. +t contains bile salts, which inhibit gram positive bacteria. +t produces greenish colonies with black centers if the bacterium grown is $almonella, and produces bright orange colonies when /nterobacter is produced. The Blood "gar -ate is a plate of differential medium. +t is enriched with sheep blood, and is used to see growth of bacteria and observe different types of hemolysis caused by growing bacteria. "lpha hemolysis, partial decomposition, is evident with green discoloration. Beta hemolysis, complete decomposition, is seen with clearing around the colony. !amma hemolysis, no decomposition, shows no clearing or discoloration, but growth can be seen. The Brilliant !reen "gar -late is a plate of selective medium. +t produces growth of many $almonella species. !rowth of all gram*positive and most gram negative bac teria is inhibited. +t also shows differentiation between lactose fermenters, which could be /. coli and non*lactose fermenters, $almonella. 7ellow growth shows evidence on lactose fermenting bacteria, while dark red shows non*lactose fermenting bacteria. Mac0onkey agar plate uses crystal violet to inhibit the growth of !ram -ositive Bacteria, and permits the growth of !ram 8egative Bacteria, also containing sugar lactose and Bile salts. +ts p indicator is neutral red. This agar differentiates bacteria on their ability to ferment lactose sugar as well. 9actose fermenting bacterium produces pinkish colonies, while non*fermenting bacteria produces purple colonies. The Tryptic $oy "gar -late is a standard plate which will be used as a control medium to compare the other plates to. Materials
"ll of the materials that were used for this procedure are listed below: *unknown bacteria sample given in li;uid tube *blood agar plate *brilliant green agar plate *Mac0onkey agar plate *Tryptic $oy "gar -late *ektoen /nteric agar -late *5ogel and 6ohnson agar -late *Mannitol $alt "gar -late */osin Methylene Blue agar -late * 9oop "pplicators
Methods
The methodology that was exercised for this lab procedure was the streak plate techni;ue on the various selective and differential media that we identified in class.
5. Results !pts"
&igure >: Blood "gar -late $light green discoloration shows that alpha hemolysis, or partial decomposition, has occu rred. 3this may suggest that the bacteria could possibly be B. med or $trep. -
&igure 2: Brilliant !reen "gar -late The brilliant green agar plate shows very po or to no growth at all. This rules out salmonella, and possibly /. 0oli
&igure ?: Mac0onkey "gar -late This plate shows clear, translucent colorless colony growth, suggesting that whatever bacteria that have grown on this plate did not form any lactic acid, making it non*fermenting bacteria.
&igure 4: ektoen /nteric "gar -late This plate shows some blackish green formation where the un known was streaked.
&igure (: 5ogel 6ohnson "gar -late This plate shows no growth at all, ruling out the possibilities of the bacteria being $. aureus, B. Meg, and $taph. ", which would have shown different results.
&igure @. Mannitol $alt "gar The strong yellow colonies suggest that the bacterium does produce an acidic byproduct due to the fact that it changed the color of the p indicator in the Mannitol $alt "gar. "lso, looking solely at this plate, this suggests that the bacteria can possibly be B. meg or $taph ".
&igure ': /osin*Methylene Blue "gar -late This agar plate shows translucentAamber colonies, which suggest that the bacteria c an possibly be salmonella, which does not produce lactose.
&igure . T$" -late, control, basic medium
Aar $late Blood "gar
Results "lpha emolysis
$ossible %rown Bacteria *$trep. -
Brilliant !reen "gar Mac0onkey "gar
8o !rowth 0olorless Translucent
*B.Meg & 8ot $almonella, possibly not /.0oli &$almonella
ectoen /nteric 5ogel 6ohnson Mannitol $alt "gar
0olonies Blackish !reen formation 8o !rowth 7ellow 0olonies
&$almonella & 8ot B. Meg, $taph. ", or M. $meg &"cid producing $taph ".
TranslucentA"mber
*"cid producing B. Meg &$almonella
/MB "gar
0olonies Table >: esults 0hart 'iscussion
The results that came from the differential and selective agar plates were incredibly inflicting with one another, suggesting that the agar plates were contaminated during or after the procedure were done. &or example, the $alt*mannitol agar clearly shows evidence of an acid producing bacteria, but many other plates suggest the growth of $almonella, which is a non*lactose producing bacteria. + believe that the plates were probably contaminated and in contact with "cid producing B. Meg bacteria, as some plates suggest the growth of B. Meg. The 5ogel 6ohnson plate was probably not contaminated, which is the reason as to why it did not show any growth. Because many of the plates suggest that $almonella was produced, my guess is that the original unknown bacterium was $almonella. The Brilliant !reen "gar results do conflict this conclusionC however, when observing the pictured results, the plates seems to be absolutely e mpty, with no evidence of any original smearing, unlike the other plates, which may suggest that due to some human error on my part, this plate did not properly have the unknown applied.
