After Gram-staining our mystery bacteria last week, we
initially suspect that our bacteria is Gram-positive due to many observed characteristics.
Below is a photograph through a microscope of what we are basing our
observations on. Our bacterium appears to be stained purple, which is a result
of uptake of crystal-violet stain. The purple stain indicates a thick layer of
peptidoglycan in the cell wall. The bacterium possesses a diplobacilus rod shape.
Gram staining results
To verify our results, we used a MacConkey
agar to determine whether our mystery bacterium found in the soil is
Gram-negative or Gram-positive. We compared our mystery bacterium to three
controls: Bacillus megaterium, which
was a Gram-positive control, Pseudomonas
aureoygynosa, which was a Gram-negative, non-lactose fermenting control,
and Klebsiella pneumonia, a
Gram-negative, lactose-fermenting control. Below is a photograph of our
MacConkey agar, showing our results for growth on the agar for our controls and
our bacterium. Our bacterium, according to our results on the MacConkey agar,
is Gram-positive, indicating that our bacterium did not grow on the agar.
MacConkey agar
Gram-positive cell walls have a thick layer of peptidoglycan with teichoic
acids, a polyalcohol. On the other hand, the cell wall of a bacterium that is
Gram-negative will have a thin layer of peptidoglycan, with a bilayer membrane
on the outside of the peptidoglycan. This bilayer membrane is composed of
phospholipids, proteins, and lipopolysaccharides.
Although we are concerning ourselves here with bacterium
found in soil outside, Gram-negative bacteria and Gram-positive bacteria are
prevalent in our every day society. These bacterium are the cause of common
infections found in almost all hospitals. Gram-negative bacterium cause many infections,
such as pneumonia, bloodstream infections, wound infections, surgical site
infections, and meningitis. Gram-negative bacteria exhibit multi-drug
resistance to many antibiotics (CDC, 2011; Moehring & Anderson, 2014).
According to the CDC, Gram-negative bacteria have built-in systems that are
able to be resistant and are able to pass along genetic information that will
allow other bacteria to also become drug-resistant. Antibiotics for
Gram-negative bacterial infections differ from those of Gram-positive due to
the risk of septic shock, morbidity, and mortality in patients. Gram-positive
bacteria also pose a threat as they are becoming increasingly resistant to
antibiotics used to treat infections caused by Staphylococcus aureus and Enterococcus
spp. (Woodford & Livermore, 2009). More commonly known as MRSA, this
Gram-positive bacteria spreads rapidly throughout hospitals. Both Gram-positive
and Gram-negative exhibit multidrug resistance to antibiotics and
antimicrobials aimed to control and eliminate bacterial infections.
“Gram-negative Bacteria
Infections in Healthcare Settings.” Centers for Disease Control and Prevention.
Centers for Disease Control and Prevention, 17 Jan. 2011. Web. 02 Mar. 2015.
Moehring, R., D.
Anderson, “Gram-negative Bacillary Bacteremia in Adults” Gram-negative
Bacillary Bacteremia in Adults. N.p., 31 Oct 2014. Web. 02 Mar. 2015.
Woodford, N., DM.
Livermore, (2009) Infections caused by Gram-positive bacteria: a review of the
global challenge. J Infect. 59, 60003-7.
No comments:
Post a Comment