BI276 Life on Earth: Microbes
Basic Principles of Microbiology: Ch 1
• Is the study of microorganisms(single-celled microscopic organisms including viruses)
2. Evolution- is the change in the inherited characteristics of biological populations
over successive generations
3. Ecology- is the scientific study of interactions among organisms and their
environment, such as the interactions organisms have with each other and with
their abiotic(non-living) environment.
• What is the science of microbiology all about?
1. Microbiology is about microbial cells and how they work, especially the bacteria,
a very large group of very small cells that, collectively, have enormous basic and
2. Microbiology is about diversity and evolution of microbial cells, about how
different kinds of microorganisms arose and why.
• The Science of Microbiology revolves around two interconnected themes
1. Understanding the living world of microscopic organisms
Microbes are excellent models for understanding cellular processes in
unicellular and multicellular organisms.
• Can grow rapidly in large numbers in small scale lab cultures.
2. Applying our understanding of microbial life processes for the benefit of
humankind and planet earth.
Microbes play important roles in medicine, agriculture, and industry
Casual agents of diseases
Digestive process, recycling of major nutrients elements.
Food industry (safety, processing)
• Microorganisms are independent entities(carry out life processes independently) • Properties of Cellular life
1. What essential properties characterize cells?
All cells show some form of metabolism, they take up nutrients from the
environment and transform them into new materials and waste products.
During these transformations, energy is conserved in a form that can be
drawn upon by the cells to support the synthesis of key structures.
The final result of any cell’s metabolic activities is to form two cells, in
microbiology we use the term growth rather than reproduction to refer
to the increase in cell number from cell division.
Cells undergo evolution, the process of descent with modification in
which genetic variants are selected based on their reproduction fitness, this
process is typically slow, but it can occu rapidly in microbial cells when
selective pressure is strong.
• Example: the selection for antibiotic resistance in pathogenic
(disease-causing) bacteria by the indiscriminate use of antibiotics
in human and veterinary medicine.
Many cells are capable of Motility, basically self propulsion. This allows
cells to move away from danger or unfavorable conditions and to exploit
new resources or opportunities.
Some cells undergo differentiation, which may, ex: produce modified
cells specialization for growth, dispersal or survival.
Some cells respond to chemical signals in their environment including
those produced by other cells of either the same or different species; this is
what thus say that cells exhibit communication.
• So, the properties of cellular life are: Evolution, Reproduction (Growth), Motility,
Differentiation, and Communication.
• Properties of all cell
1. Compartmentalization and metabolism: a cell is a compartment that takes up
nutrients from the environment, then transforms them, and releases wastes into
the environment. The cell is thus an open system.
2. Growth: Chemicals from the environment are turned into new cells under the
genetic direction of preexisting cells.
3. Evolution: Cells contain genes and evolve to display new biological properties.
Phylogenetic trees show the evolutionary relationships between cells.
• Properties of some cells 1. Motility: Some cells are capable of self propulsion.
2. Differentiation: some cells can form new cell structures such as a spore, usually
as part of cellular life cycle.
3. Communication: Many cells communicate or interact by means of chemicals that
are released or taken up.
• Cells coordinate their catalytic and genetic functions to support cell growth.
In the events that lead up to cell division, all constituents in the cell
double. This requires that a cell’s catalytic machinery, its enzymes, supply
energy and precursors for the biosynthesis of all cell components, and