Bio 122 questions and answers
microbiology ✔The study of organisms too small to be seen clearly by the unaided eye,
i.e. microorganisms
Microorganisms (microbes) include ✔Viruses - Bacteria/Archaea - protists - algae -
fungi
Non cellular - prokaryotes
Where do they live? ✔Microbes are almost everywhere!
Soil, air, col climate, hot springs, the sea, rivers and lakes, surface of plants and
animals and humans
In nature, microorganisms exist in populations ✔Mixed populations (microbial
communities)
Bacteria interact with each other and with other organisms (competition/cooperation)
Activities - alter their environment
Most of the biomass on earth is microbial
(Estimates of the total number of microbial cells on Earth is on the order of 5 1030
cells).
Microbiology revolves around two main themes ✔The basic science of life - easy to
study
Impact on humans either directly or indirectly -
devise ways to increase the benefits of microbial activity or curtail their harmful affects.
What are the impacts of microbes on humans?
Disease ✔Worldwide, infectious diseases are the leading cause of death of children
and adolescents, and one of the leading causes in adults.
Three of the top ten causes of death, or sixteen percent of all deaths each year, are
from infectious diseases . Most of these deaths are in low- and middle-income countries
and are attributable to preventable or treatable diseases such as diarrhea, lower
respiratory infections, HIV/AIDS, tuberculosis, and malaria. While significant advances
have been made in interventions to prevent and treat most of these diseases, those
interventions are often unavailable to the populations most in need.
Food ✔Benefits
Food materials that benefit from or even require microbiological activity: yogurt, cheese,
vinegar, sauerkraut, certain sausages, beer, wine ...
Problems:
Microbes grow well in food fit for human consumption: preservation to avoid
,Food spoilage
Food borne disease
N2 fixation ✔bacteria use atmospheric N to synthesise NH3: reduced need for costly
and polluting fertilizer
Nutrient cycling ✔- Microorganisms play a key role in nutrient cycling: convert nutrients
into forms readily accessible to plants
Animal husbandry ✔- Microorganisms in the rumen of cattle and sheep degrade the
cellulose present in grass and other plants
Energy/Environment ✔methanogenic bacteria produce natural gas (methane = CH4)
waste products and surplus grain can be converted to biofuels (methan, ethanol,
butanol ...)
Bioremediation: microbes clean up pollution (by degrading the pollutants: spilled oil,
pesticides etc.)
Industrial microbiology and biotechnology ✔Microbial production of amino acids,
vitamins, enzymes. Biotechnology - genetically modified microorganisms synthesize
products of high commercial value. Biotechnology: genetically modified microorganisms
synthesise products of high commercial value (e.g. insulin, human growth hormone)
The Impact of Microorganisms on Humans ✔Microorganisms can be both beneficial
and harmful to humans
We tend to emphasize the harmful microorganisms (i.e. as infectious disease agents =
pathogens), but many more microorganisms in nature are beneficial than are harmful.
Robert Hooke was the first to describe microorganisms (1665) ✔A drawing by Robert
Hooke (1665) - a bluish coloured mold growing on the surface of leather
Antoni van Leeuwenhoek ✔was the first to describe bacteria (1676)
Germ vs Miasma theory
in the mid 1800s ✔Miasma theory-'bad air' origin of epidemics from rotting organic
matter; get rid of the smells you get rid of the illness such as cholera or 'plague'
Eradication of disease through the preventive approach of cleansing and scouring.
One prominent supporter of the miasma theory was Dr. William Farr also Florence
Nightingale. Farr was convinced that cholera was transmitted by air. Soil at low
elevations, especially near the banks of the River Thames, contained much organic
matter which produces miasmata. The concentration of such deadly miasmata would be
greater at lower elevations than in communities in the surrounding hills.
Miasma personal protective equipment! ✔Mask with
Scented herbs
,Pokey stick
Mal aria
'Bad air'
Hat
Long coat
Improved microscopes became only available in the 19th Century. ✔Microbiology
blossomed in the mid to late 19th century, as a result of scientists focussing on two
major question:
Is there spontaneous generation of life?
What is the nature of infectious diseases?
Is there spontaneous generation of life? ✔flask unsealed vs flask sealed
Louis Pasteur (1822-1895) ✔disproved the concept of spontaneous generation
(hypothesis that living organisms can originate from non living matter)
His work led to the development of methods for controlling the growth of
microorganisms:
- sterilisation (killing of all microorganisms including dormant forms)
- pasteurisation (destruction of vegative organisms, but not spores, by brief heating)
- developed vaccines against anthrax and rabies
Robert Koch (1843-1910) ✔What is the nature of infectious disease?
Microbes were "suspects" but proof was lacking!
Established germ theory of disease.
Formulated criteria for proving that a specific microorganism causes diseases: "Koch's
Postulates"
Developed simple methods for obtaining bacteria in pure culture
Obtained pure cultures by streaking samples on nutrient solutions solidified with gelatin
or agar
Bacterial and fungal colonies on solid media
Koch's Postulates (criteria for proving that a specific microorganism causes disease) ✔
Suspected causative agent must be found in every case of the disease and be absent
from the healthy host
Agent must be isolated and grown outside the host
When the agent is introduced into a healthy, susceptible host, the host must get the
disease
The same agent must be re-isolated from diseased experimental host
Led to discovery of the causes for:
Anthrax
Tuberculosis
Cholera
, Koch awarded Noble prize for Physiology and Medicine (1905)
From 2 kingdoms to 3 domains ✔Prokaryotes = "bacteria"
All known disease-causing prokaryotes belong to the Bacteria domain
properties of all cells ✔compartmentalisation and metabolism, growth, evolution,
properties of some cells ✔motility, differentiation, communication
Typical sizes ✔Viruses 0.01 - 0.2 μm
Bacteria 0.2 - 5 μm
Eukaryotes 5 - 100 μm
Yeast 5 - 10 μm
Algae 10 - 100 μm
Protozoa 50 - 1000 μm
In general! The very largest can be up to 750 um but the vast majority are small.
Surface area to volume benefits.
Importance of cell volume ✔Higher s/v ratio of smaller cells= faster rate of nutrient
exchange compared to large cells
Smaller cells = faster growth
Evolution/mutation rates, more cells/growth > more mutations may lead to greater
evolutionary possibilities
Eukaryotic cell structure ✔Nucleus - membrane enclosed
(contains DNA)
Endoplasmatic
Reticulum (ER; protein glycosylation, membrane factory, lipid synthesis)
Mitochondrion
(respiration)
Golgi apparatus
(modifies, stores,
routes products of the ER)
Cytoplasmic membrane
(separates cytoplasm
from the outside)
Cell wall (plants & fungi; gives structural strength)
Ribosomes
(protein synthesis)
Ribosomes site of protein synthesis. S svedberg units. Prokaryotes 70S ribosomes;
Eukaryotes 80S ribosomes
Bacterial cell structure ✔S-layer - layer of proteinfunction not fully understood -
crystalline
