BIOSCI 221- TEST QUESTIONS AND ANSWERS
LATEST UPDATE
WHAT IS A MICROBE?
A microbe is a microscopic organism - commonly defined as a living organism that
requires a microscope to be seen.
They can be unicellular (ex: most protist or bacteria) or multicellular
Cell
- A cell is the smallest unit of life composed of a membrane-enclosed compartment.
- Microbial cells range in size from millimeters down to 0.2 micrometers.
Viruses
- noncellular microbes that can be up to ten times smaller than a cell.
- A virus needs a cell to replicate in
PROKARYOTES VS EUKARYOTES
Microbial cells may be:
1) Prokaryotic (Bacteria or Archaea):
- No true “nucleus” or nuclear membrane
- Prokaryotes include bacteria and archaea.
2) Eukaryotic:
- Have a true nucleus
- Eukaryotic microbes include some types of fungi, protozoa, and algae
Definition of Microbe: Contradiction
Some protists and algae can be seen by the naked eye but are considered to be a
microbe
Microbe Size Comparison
Classifying Microbes
- Microbes, like other organisms, are classified as members of a species according to a
shared set of genes and traits.
- Microbes are classified by their genetic relatedness determined by comparing
microbial genomes (a genome is the total DNA content of an organism)
a) The more closely related two organisms are, the more recently they diverged from a
common ancestor
b) Relatedness is important for understanding how microbes respond to treatment (Ex:
An antibiotic that targets an intestinal pathogen may also kill beneficial bacterial living in
the intestines leading to digestive issues)
Viruses- Are they Microbes?
Currently not considered microbes:
- Noncellular
- Nonmetabolic: They depend on the host metabolism to generate more viruses
- Unable to reproduce independently: Invade cells, which produces new viruses
- Genes aren’t always made of DNA
,- Are viruses alive? This is a subject of debate
Microbial diseases devastate human populations
- Throughout history, microbial diseases such as tuberculosis and leprosy have
profoundly affected human demographics and cultural practices.
- Before the 1850s the role of microbes as infectious agents was unknown.
The first compound microscope
- Robert Hooke built the first compound microscope in the mid 1600s
· This allowed for the discovery of microorganism
· An illustration of mold sporangia, drawn by Hooke in 1665, from his observations of
objects with a compound microscope.
Leeuwenkoek’s stronger lens observations
- Developed ground lenses stronger than Hooke's
- Anton van Leeuwenhoek observed bacteria with a single-lens microscope - he was the
first to observe bacterial cells
- It took nearly another 200 years before a connection was made between microbes and
human diseases.
Pasteur’s Proof
- Louis Pasteur(1822-1895) a famous French microbiologist disproved spontaneous
generation
- Showed that individual microbial strains had unique properties and demonstrated that
fermentation is caused by microorganisms.
- Louis Pasteur proved that bacteria were living things capable of reproducing and
potentially acting as a cause of disease.
Germ Theory of Disease: Foundation
- In 1856, Pasteur discovered properties of fermentation by microorganisms, and that
airborne microbes were the cause of food spoilage.
- He suggested that if microbes were responsible for food spoilage and fermentation,
they could also be responsible for causing infection.
- This was the foundation for the germ theory of disease.
Microbes can lead to disease
- Specific diseases are caused by microscopic "germs."
- Disease is common in overcrowded areas like cities and during warfare
Infectious disease linked with Mortality
- The field of public health assesses the role of infectious disease in the health of
populations.
- Epidemiologists use statistics to determine the cause of disease using methods first
implemented by Nightingale.
- In the United States, public health is monitored by the Centers for Disease Control
(CDC).
Morbidity and Mortality
Public health agencies track disease rates and severity:
- Morbidity is the rate of illness due to a disease.
- Mortality is the rate of death due to a disease.
, The Centers for Disease Control and Prevention (CDC) publishes the Morbidity and
Mortality Weekly Report, which discusses current outbreaks, statistics, and other health
topics affecting people in the United States.
Infection to Diagnosis
- Diagnosis requires direct evidence that a given microbe caused the disease
- Robert Koch worked on this problem in the nineteenth century
- Koch was the first to establish that anthrax was caused by a microbial infection.
- Growth of Microbes in pure culture:
· Pure cultures grown from a single colony
Koch’s Postulate
Koch developed the first scientific method for establishing the microbial cause of a
disease and won the Nobel Prize in 1905 for this work.
The 4 criteria:
1) The microorganism must be found in diseased but not healthy individuals
2) The microorganism must be cultured from the diseased individual
3) Inoculation of a healthy individual with the cultured microorganism must recapitulate
the disease
4) The microorganism must be re-isolated from the inoculated, diseased individual and
matched to the original microorganism.
Koch’s Postulate: Exception
- M. tuberculosis causes symptoms in only 10 percent of people infected.
- HIV is difficult to detect in early stages and is an exclusively human pathogen.
Therefore, following the postulates would involve infecting human subjects with HIV,
which is highly unethical
Human Body and Microbes
Many areas of the human body are colonized with microbes. The collection of all
microbes on the human body is called the human microbiota
Colonization refers to the ability of the microbe to stay attached to the body surface
and replicate.
Adhesins enable the microbiota to attach to host cells.
Gut Microbiome
- Made up of trillions of bacteria, fungi and other microbes
- Extremely important for your health
MICROBES SUPPORT NATURAL ECOSYSTEMS
Sergei Winogradsky was one of the first scientists to study microbes in their natural
habitats.
Marshes/wetlands support bacteria known as lithotrophs, which feed on inorganic
molecules.
Winogradsky developed enrichment culture methods and selective growth media to
grow some bacteria while excluding others.
Wetlands Microbiome
LATEST UPDATE
WHAT IS A MICROBE?
A microbe is a microscopic organism - commonly defined as a living organism that
requires a microscope to be seen.
They can be unicellular (ex: most protist or bacteria) or multicellular
Cell
- A cell is the smallest unit of life composed of a membrane-enclosed compartment.
- Microbial cells range in size from millimeters down to 0.2 micrometers.
Viruses
- noncellular microbes that can be up to ten times smaller than a cell.
- A virus needs a cell to replicate in
PROKARYOTES VS EUKARYOTES
Microbial cells may be:
1) Prokaryotic (Bacteria or Archaea):
- No true “nucleus” or nuclear membrane
- Prokaryotes include bacteria and archaea.
2) Eukaryotic:
- Have a true nucleus
- Eukaryotic microbes include some types of fungi, protozoa, and algae
Definition of Microbe: Contradiction
Some protists and algae can be seen by the naked eye but are considered to be a
microbe
Microbe Size Comparison
Classifying Microbes
- Microbes, like other organisms, are classified as members of a species according to a
shared set of genes and traits.
- Microbes are classified by their genetic relatedness determined by comparing
microbial genomes (a genome is the total DNA content of an organism)
a) The more closely related two organisms are, the more recently they diverged from a
common ancestor
b) Relatedness is important for understanding how microbes respond to treatment (Ex:
An antibiotic that targets an intestinal pathogen may also kill beneficial bacterial living in
the intestines leading to digestive issues)
Viruses- Are they Microbes?
Currently not considered microbes:
- Noncellular
- Nonmetabolic: They depend on the host metabolism to generate more viruses
- Unable to reproduce independently: Invade cells, which produces new viruses
- Genes aren’t always made of DNA
,- Are viruses alive? This is a subject of debate
Microbial diseases devastate human populations
- Throughout history, microbial diseases such as tuberculosis and leprosy have
profoundly affected human demographics and cultural practices.
- Before the 1850s the role of microbes as infectious agents was unknown.
The first compound microscope
- Robert Hooke built the first compound microscope in the mid 1600s
· This allowed for the discovery of microorganism
· An illustration of mold sporangia, drawn by Hooke in 1665, from his observations of
objects with a compound microscope.
Leeuwenkoek’s stronger lens observations
- Developed ground lenses stronger than Hooke's
- Anton van Leeuwenhoek observed bacteria with a single-lens microscope - he was the
first to observe bacterial cells
- It took nearly another 200 years before a connection was made between microbes and
human diseases.
Pasteur’s Proof
- Louis Pasteur(1822-1895) a famous French microbiologist disproved spontaneous
generation
- Showed that individual microbial strains had unique properties and demonstrated that
fermentation is caused by microorganisms.
- Louis Pasteur proved that bacteria were living things capable of reproducing and
potentially acting as a cause of disease.
Germ Theory of Disease: Foundation
- In 1856, Pasteur discovered properties of fermentation by microorganisms, and that
airborne microbes were the cause of food spoilage.
- He suggested that if microbes were responsible for food spoilage and fermentation,
they could also be responsible for causing infection.
- This was the foundation for the germ theory of disease.
Microbes can lead to disease
- Specific diseases are caused by microscopic "germs."
- Disease is common in overcrowded areas like cities and during warfare
Infectious disease linked with Mortality
- The field of public health assesses the role of infectious disease in the health of
populations.
- Epidemiologists use statistics to determine the cause of disease using methods first
implemented by Nightingale.
- In the United States, public health is monitored by the Centers for Disease Control
(CDC).
Morbidity and Mortality
Public health agencies track disease rates and severity:
- Morbidity is the rate of illness due to a disease.
- Mortality is the rate of death due to a disease.
, The Centers for Disease Control and Prevention (CDC) publishes the Morbidity and
Mortality Weekly Report, which discusses current outbreaks, statistics, and other health
topics affecting people in the United States.
Infection to Diagnosis
- Diagnosis requires direct evidence that a given microbe caused the disease
- Robert Koch worked on this problem in the nineteenth century
- Koch was the first to establish that anthrax was caused by a microbial infection.
- Growth of Microbes in pure culture:
· Pure cultures grown from a single colony
Koch’s Postulate
Koch developed the first scientific method for establishing the microbial cause of a
disease and won the Nobel Prize in 1905 for this work.
The 4 criteria:
1) The microorganism must be found in diseased but not healthy individuals
2) The microorganism must be cultured from the diseased individual
3) Inoculation of a healthy individual with the cultured microorganism must recapitulate
the disease
4) The microorganism must be re-isolated from the inoculated, diseased individual and
matched to the original microorganism.
Koch’s Postulate: Exception
- M. tuberculosis causes symptoms in only 10 percent of people infected.
- HIV is difficult to detect in early stages and is an exclusively human pathogen.
Therefore, following the postulates would involve infecting human subjects with HIV,
which is highly unethical
Human Body and Microbes
Many areas of the human body are colonized with microbes. The collection of all
microbes on the human body is called the human microbiota
Colonization refers to the ability of the microbe to stay attached to the body surface
and replicate.
Adhesins enable the microbiota to attach to host cells.
Gut Microbiome
- Made up of trillions of bacteria, fungi and other microbes
- Extremely important for your health
MICROBES SUPPORT NATURAL ECOSYSTEMS
Sergei Winogradsky was one of the first scientists to study microbes in their natural
habitats.
Marshes/wetlands support bacteria known as lithotrophs, which feed on inorganic
molecules.
Winogradsky developed enrichment culture methods and selective growth media to
grow some bacteria while excluding others.
Wetlands Microbiome
