5
What is a bacteriophage?
A bacteriophage or phage, a nucleic acid molecule that is surrounded by a protein structure, is a type of virus that infects bacteria. Unable
to replicate by itself, the virus attaches to a bacterium with the intention of infecting and ultimately destroying its host cell. Once that
happens, the phage forces the cell to produce viral components rather than bacterial components. In a process known as lysis, new phages
assemble and burst out of the bacterial host, sometimes removing a portion of their host’s bacterial DNA.
Phages were discovered between 1915 and 1917 by Frederick Twort and Felix D’Herelle but not fully visualized until the 1940s with the
invention of the electron microscope. Today, bacteriophage researchers are developing engineered viruses to overcome antibiotic resistance
and are creating experimental phage cocktails to treat diseases.
How does a TEM work,
exactly?
Producing a significantly higher resolution than
that of light telescopes, a TEM works by transmitting
a beam of electrons through a sample specimen.
During transmission, electrons interact with the sample
which is suspended on a special grid to produce an
incredibly detailed image. The sample itself is typically
less than 100 nanometers in thickness. (For reference,
a sheet of paper is approximately 100,000
nanometers thick.) After
the transmission, the
image of the sample
is magnified.
Sowoolu, a General Studies major, extracts
her sample in ACM’s Microbiology Lab the
morning of the trip to UMBC.
by making webbed Petri plates
to extract a phage sample. It was
repetitive and not without frustrations
along the way. They knew that the
TEM would be the only way to
potentially view their phage for the
first time.
After arriving at UMBC, Barmoy,
an UMBC alumna and parent of a
current UMBC student, led them
to the Biological Sciences Building
that housed the TEM, explaining the
layout of campus during her informal
tour. Following introductions,
the students received one-onone
instruction with Dr. Tagide
deCarvalho, a UMBC research
assistant professor and manager of
the Keith R. Porter Imaging Facility.
Using an assortment of pipettes,
lab bottles, tweezers and Wat paper,
they placed their bacteriophage
samples on electron microscopy
grids, cleared off debris, and carefully
stained them using uranyl acetate.
In the crowded room containing
the TEM, the students watched as
deCarvalho placed each individual
grid in the TEM and slowly navigated
the TEM’s viewer to focus on the
magnified but grainy black and white
sample for a phage among the
sample’s debris. It was painstaking
work, sometimes requiring multiple
sample preparations, but when the
outline of a bacteriophage came into
focus, the students’ expressions
were ones of amazement and relief.
Every aspect of the UMBC lab
experience was a teaching moment.
One student learned that filtering her
sample twice led to the collapsed
“heads” of bacteriophages in her
sample. Two students, long-time
friends from high school, vied for
bragging rights on who had the best
sample with deCarvalho.
Using a camera attached to
the FEI Morgagni 268 100 kV
TEM, deCarvalho photographed
and saved the phage images for
electronic transmission. Later in
the week, students would use the
TEM-produced images to measure
their phages and report their
findings to the Actinobacteriophage
Database. Their findings would be
supplemented by DNA information
extracted during the last week of
fall semester classes.
With their mission accomplished
and sense of relief now present
among the students, the group had
lunch at the Student Union after a
surprise visit from an ACM science
student who had transferred to
UMBC. Before returning to the
college van for the ride home, they
detoured to see one more invaluable
asset at UMBC: True Grit, a bronze
statue of the school’s Chesapeake
Bay Retriever mascot.