Introduction To Microbiology Flashcards
What does “microbiology” mean?
microbiology = knowledge of small life forms, not just bacteria
What is “small”?
Eukaryotic cells are generally 10,000 to 100,000 times the size (= volume) of their Bacterial and Archaeal counterparts
Smaller cells sometimes “sit” on larger cells
Key definitions
➢ Microorganism: An organism too small to be seen except
with the aid of a microscope.
➢ Microbiology: The branch of science that deals with
microorganisms.
➢ Microbiome: The totality of microorganisms and their
collective genetic material present in or on the human body
or in another environment.
Categorisation of Life Forms
n 1735 Linnaeus divided life into two kingdoms:
➢ Vegetabilia
➢ Animalia
The Five-kingdom system classification (1969)
➢ This is one of many
classification systems that
developed from the Linnaean
view.
➢ This classification is based on
appearance of the organisms –
is not based on their genetic
properties!
➢ And is not valid anymore
Flaw of the five-kingdom system
The Five-kingdom system classification is based on appearance of the
organisms – is not based on their genetic properties
What does this mean? For example: Protista vs Monera
Monera: Any unicellular organism without a nucleus.
Referred to as prokaryotes.
From the Greek: Pro-, before; karyon, nut or kernel. Meaning “without a nucleus”.
Protista: Any eukaryotic organism that is not an animal, plant or fungus.
How to classify organisms by using genetics?
➢ All life on Earth has ribosomes (and
therefore rRNA genes)
➢ These rRNA genes are reasonably large
genes, containing a lot of information
➢ They contain regions of near universal
sequence conservation.
➢ Comparing sequences reveals which
organisms more closely related.
How did the eukaryotic cells evolve?
The gene content view: Fusion between a Bacterium and an Archaeon.
α-proteobacterium
Mitochondrion progenitor
The Archaeal Ancestor
➢ In 2015 the Lokiarchaeota, a clade of Archaea found in deep marine
sediments, were identified.
➢ This group of archaea appeared to be most closely related to Eukaryotes.
➢ This discovery was exploited to search for other related organisms, forming
the Asgard clade.
Whats a clade?
Branch in a phytogenic tree
representing a monophyletic group - includes
organisms (e.g., species) consisting of all the
descendants of a unique common ancestor.
The Asgard Clade
Members include:
* Lokiarchaeota
* Thorarchaeota
* Odinarchaeota
* Heimdallarchaeota
Seems “we” are most closely related to Heimdallarchaeota.
A few old terms (no longer used)
➢ Protista: any eukaryotes which are not
plants, animals, or fungi → now
recognised as eukaryotic microbes
➢ Monera: unicellular organisms without a
nucleus → Later called Prokaryotes, and
now split as Bacteria and Archaea
➢Archaeabacteria: old name for Archaea
➢ Eubacteria: old name for Bacteria
Skin Microbiome
There may be as many as 10^7 bacteria per cm2 on the face and armpit, more like 100 per cm2 on
the forearms.
➢ Not detrimental to health and may protect us from colonisation by pathogens.
➢ Problems caused by bacteria include acne, dandruff and MRSA.
➢ Corynbacteria have a role in body odour
The gut microbiome
gut microbiome may play a role in a number of
diseases.
This may present new opportunities for diagnosis,
prognosis, and treatment of a variety of human
diseases.
* Cardiovascular disease
* Irritable bowel disease
* Clostridium difficile infection
* Inflammatory bowel disease
* Cancer
EPEC: Enteropathic E. coli
Most strains of Escherichia coli are
components of the microbiota -
and are not pathogenic.
However, some strains are
pathogenic = they produce
toxins = they cause disease.
The Black Death – Yersinia pestis
➢Yersinia pestis is a Gram-negative, non-motile, rod-shaped coccobacillus.
➢It can infect humans via the oriental rat flea.
➢The disease takes three main forms: bubonic (most common – infection of
the lymph nodes), pneumonic (infection of the lungs), and septicemic
(infection of the blood).
➢Symptoms: fever, headache, chills, and weakness. Swollen lymph nodes
(buboes) in bubonic plague.
➢Very high mortality rate: ~50% without treatment
The Black Death Pandemics
The Justinian Plague Began
in 541 AD.
Frequent outbreaks over the
next two hundred years.
Over 25 million people
killed,
Affected virtually all of the
known world at that time
The Black Death
Began in Europe in 1347
Within 4 years killed 75
million people, one third of
the population of Europe.
Over the next 75 years
returned at least once every
eight years.
The Modern Plague
Began in China in the 1860s
Over 20 years, it spread to
port cities around the world.
Killed about 10 million
people.
Cause and transmission
identified at this time.
The Black Death – Impact on society
➢ Black Death helped intensify religious and political upheaval in 14th century.
➢ Although a disaster, population drop created a Europe with less competition
for food, work and shelter.
➢ Massive labour shortages sped up the development of many economic,
social, and technical modernizations
➢ Even been considered a factor in the emergence of the Renaissance in the
late 14th century.
➢ Renaissance critical to the shape and character of Europe as we know it.
Epidemic Typhus – Rickettsia prowazekii
➢ Rickettsia prowazekii, a Gram-negative, rod-shaped, obligate
intracellular bacterium,
➢ It is the causative agent of epidemic typhus.
➢ Phylogenetically closely related to mitochondria.
➢ Transmitted by lice, spread is greatly facilitated by overcrowding.
➢ R. prowazekii effects are worst in individuals suffering from malnutrition
and other burdens such as exhaustion. Both conditions met in wars:
mobilisation of troops and movement of refugees
The great famine –
Phytophthora infestans (a fungus)
➢ The 1843 potato harvest was a good one. The following spring surplus tubers,
some diseased, were dumped onto the soil.
➢ 1844, cold wet weather ideal for infection dominated, the harvest failed, and by
the winter people were starving.
➢ 1845 was worse, and typhoid fever and dysentery also appeared.
➢ In 1845 Ireland had a population of 8 million, reduced to 5 million within a few
years. The Irish population surpassed 5 million for the first time since the famine
in April 2021.
AIDS - HIV
➢ HIV is a retrovirus,
➢ It integrates into the host genome.
➢ Deaths worldwide at peak (2005): 1.9 million.
➢ Deaths in 2019: about 690,000.
➢ As of 2019 approximately 38 million people have
HIV worldwide.
➢ Approximately 25% of people do not know they
are infected (2016).
➢ When treated, prognosis is for a near normal life
span.
Serratia marcescens
Characteristics
Appearance: A pink, orange, or red discoloration that’s visible to the naked eye
Shape:
A rod-shaped bacteria that stains pink under a microscope
Antibiotic resistance: Many strains are resistant to multiple antibiotics
Causes of infection
Contaminated medical devices: S. marcescens can contaminate respiratory equipment and catheters
Poor catheterization techniques: Improperly inserted catheters can lead to infection
Injection drug use: People who use injection drugs are at a higher risk of infection
Symptoms
Urinary tract infections (UTIs) can cause dysuria, urinary frequency, and urinary urgency
Pyelonephritis can cause fever, rigors, flank pain, and delirium
Penicillium notatum
➢ Penicillium notatum (now P. chrysogenum) is
the source of several β-lactam antibiotics,
most importantly penicillin.
➢ The discovery of penicillin ushered in a new
age of antibiotics derived from
microorganisms.
Fleming was experimenting with
the influenza virus in the Laboratory of the
Inoculation Department at St. Mary’s
Hospital in London.
➢ Fleming returned from a two-week vacation
to find that a mould had developed on an
accidentally contaminated staphylococcus
culture plate.
➢ Upon examination of the mould, he noticed that the culture prevented the growth
of staphylococci
Marine Microbial Numbers
➢ Evidence suggests that the total number of microbes living in the
oceanic environment is almost half that of soil.
➢concentration is lower (far more volume of ocean).
➢ A single litre of seawater has about one billion bacteria and 10 billion
viruses.
➢ The Cyanobacteria play a key role in fixing carbon dioxide into organic
matter.
