Assalamu Alaikom everyone welcome to another ATP video. In this video we'll talk about
some basics in microbiology to get you introduced to this subject. So what is
microbiology? Microbiology: is the study of microscopic organisms such as:
bacteria, viruses, fungi, and protozoa. most of these microorganisms are beneficial
to us. In humans we have normal microbiota that helps in digestion. In
plants the bacteria is responsible for nitrogen fixation and in animals it
helps in cellulose digestion. Also these microorganisms are used in industries.
Generally we divide the organisms these bacteria viruses and fungi according to
their characteristics. So in bacteria we use Gram stain either:
positive or negative to categorize them. In viruses we depend on their genome:
DNA or RNA, whether it's single stranded or double stranded to categorize them.
In fungi they're either divided into: molds which is multicellular, or yeasts which are unicellular.
We also have the hierarchy of classification we used to
put each organism including us humans into its category "we took it in high
school if you remember". So from highest to lowest it's: domain > kingdom > phylum >
class > order > family > genus > and species. You can use this mnemonic to help you
remember Dina's kids prefer candy over fried
green spinach. Spinach is pretty underrated by the way </3. So if we start
from the top we have three domains on this planet bacteria, archaea and Eukarya.
Both bacteria and archaea are considered as prokaryotes whereas Eukarya are
considered as eukaryotes. The main differences between prokaryotes and
eukaryotes are absence of cytoplasmic structures such as mitochondria Golgi
apparatus, and endoplasmic reticulum in prokaryotes, and then we have absence of
cell wall in eukaryotes except for fungi and plants also they differ in the
structure of the ribosomes. After that we go to the kingdom both
bacteria and archaea have only one single kingdom which are bacteria and
archaea, respectively. And then we have the eukarya and it has four kingdoms:
protists, fungi, plants, and animals. And then we continue the classification like
this like we mentioned before phylum class order family genus and then species.
For now we will focus on bacteria how do we name them basic structures in gram
staining. Any bacteria's name is composed of two words: the first one refers to the
name of the genus, and the second one refers to the species name. We'll take
Staphylococcus aureus as an example. So Staphylococcus is the genus and aureus
is species. Also the name of the microorganism might refer to its shape.
Like an our example staphylo means a bunch of grapes or a cluster and coccus
means round cells aureus means it looks like gold in color when we culture. Other
than cocci the round cells we have: rods or bacilli, and then we have spirochete:
which are curved, and then we have diplococci which is basically two cocci or
basically two round cells, and then we have cocco-bacilli which is a mixture of
both a rod and a round cell, and then we have vibrios which is a curved rod, then
we have streptococci which are cocci in chains, and then we
have the staphylococci like we mentioned in our example which are large cocci in
irregular clusters, and then we have tetrads which are cocci in a packet of
four from the name tetrads tetra which means four. Now we're going to discuss
the bacterial architecture. Since bacteria are considered as cells that
means they have: genetic material, a cell membrane, and a cytoplasm. In addition to
that they have a cell wall, a flagella which is used for locomotion, and then we
have pili which is used for attachment, and then we have plasmid
which is an extra chromosome of genetic material so it's not part of the DNA, and
then we have a glycocalyx which is used for protection. The glycocalyx can be
either capsule which is neatly organized and protects the bacterium from
phagocytes, or biofilm which is an unorganized loose
structure yet important for attachment. But here also have porins these porins
are transmembrane proteins that selectively allow some molecules to pass
the cytosol of the bacteria. Porins can mediate antibiotic resistance by
inhibiting some antibiotics from entering the bacteria. They also have
Mesosomes that are equivalent to mitochondria in eukaryotes. Remember bacteria
doesn't have mitochondria so they have Mesosomes instead bacteria depend on
these Mesosomes for respiration. Mesosomes are formed by the invaginations of
a plasma membrane into the cytosol. Generally speaking this is how a bacterium
looks like; however, each bacterium has its special characteristics that
distinguish it from the rest. Now move on to gram staining. In gram staining we can
classify bacteria into either gram positive or gram negative and that
depends on the cell wall constituents and its ability to react with the Gram
stain. To classify them gram positive react with the stain and give blue color,
while gram negative react with the stain and give red or pink color. If we look at
the membranes of both gram-positive and gram-negative bacteria, from the inner
layer, we see that both of them have plasma membrane; however, on the outside
the differences start appear. In gram positive it has a thick peptidoglycan
layer. This layer has two techoic and lipotechoic acids. In gram negative
bacteria and outer to the plasma membrane we have: thin layer of
peptidoglycan, and then we have outer membrane composed of phospholipids that
has trans-proteins and lipoproteins embedded into it and the last layer in
gram-negative bacteria is a polysaccharide. The lipopolysaccharide
layer is composed of three structures: o-antigen, core polysaccharide, lipid A,
which is also known as endotoxin. So we can conclude that the endotoxins are
only present in gram-negative bacteria. These endotoxins are antigenic which
means they can elicit an immune response causing some symptoms of: fever, weakness,
aches, or shock to the patient.
So that's it for the intro hope you enjoyed!
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