GENERAL MICROBIOLOGY
MBIO 140
“…THE ROLE OF THE INFINITELY SMALL IN NATURE IS
INFINITELY LARGE"…. Louis Pasteur
Welcome to microbiology—the study of microorganisms.
1
,Microorganisms are single-celled microscopic organisms and viruses, which are microscopic
but not cellular.
What is microbiology all about?
Microbiology is about cells and how they work, especially the bacteria, a large group
of cells of enormous basic and practical importance (Figure 1.1).
Figure 1.1 Microorganisms. (a, b) A single microbial cell can have an independent
existence. Shown are photomicrographs of phototrophic (photosynthetic) microorganisms
called (a) purple bacteria and (b) cyanobacteriaand (d) bioluminescent (light-emitting) cells of
the bacterium Photobacterium leiognathi grown in laboratory culture. One milliliter of water
from the lake (c) or one colony from the plate (d) contains more than 1 billion (109) individual
cells.
Microbiology is about diversity and evolution, about how different kinds of
microorganisms arose and why.
It is about what microorganisms do in the world at large, in soils and waters, in the
human body, and in animals and plants.
One way or another, microorganisms affect all other life forms on Earth, and thus we
may think of microbiology as the foundation of the biological sciences.
Microorganisms differ from the cells of macroorganisms. The cells of
macroorganisms such as plants and animals are unable to live alone in nature and exist
only as parts of multicellular structures, such as the organ systems of animals or the
leaves of leafy plants.
2
, By contrast, most microorganisms can carry out their life processes of growth, energy
generation, and reproduction independently of other cells.
1. INTRODUCTION TO MICROBIOLOGY
1.1 Microbiology
The science of microbiology revolves around two themes:
(1) Understanding basic life processes, and
As a basic biological science, microbiology uses and develops tools for probing the
fundamental processes of life .
Scientists have been able to gain a sophisticated understanding of the chemical and
physical basis of life from studies of microorganisms because microbial cells share many
characteristics with cells of multicellular organisms; indeed, all cells have much in
common .
Moreover, microbial cells can grow to extremely high densities in laboratory culture,
making them readily amenable to biochemical and genetic study .
These features make microorganisms excellent models for understanding cellular
processes in multicellular organisms, including humans
(2) Applying our understanding of microbiology for the benefit of humankind.
As an applied biological science, microbiology deals with many important practical problems
in medicine, agriculture, and industry For example:
Most animal and plant diseases are caused by microorganisms .
Microorganisms play major roles as agents of soil fertility and in supporting domestic
animal production .
3
, Many large-scale industrial processes, such as the production of antibiotics and human
proteins, rely heavily on microorganisms. Thus both the detrimental and the beneficial
aspects of microorganisms affect the everyday lives of humans.
The Importance of Microorganisms
In this book we will see that microorganisms play central roles in both human
activities and the web of life on Earth.
Although microorganisms are the smallest forms of life, collectively they constitute
the largest mass of living material on Earth and carry out many chemical processes
necessary for other organisms.
In the absence of microorganisms, other life forms would never have arisen and could
not now be sustained. Indeed, the very oxygen we breathe is the result of past microbial
activity (Figure 1.1b).
Moreover, we will see how humans, plants, and animals are intimately tied to
microbial activities for the recycling of key nutrients and for degrading organic matter.
No other life forms are as important as microorganisms for the support and maintenance
of life on Earth.
Microorganisms existed on Earth for billions of years before plants and animals
appeared, and we will see in later chapters that the diversity of microbial life far exceeds
that of the plants and animals.
This huge diversity accounts for some of the spectacular properties of
microorganisms. For example, we will see how microorganisms can live in places
unsuitable for other organisms and how the diverse physiological capacities of
microorganisms rank them as Earth’s premier chemists.
4
MBIO 140
“…THE ROLE OF THE INFINITELY SMALL IN NATURE IS
INFINITELY LARGE"…. Louis Pasteur
Welcome to microbiology—the study of microorganisms.
1
,Microorganisms are single-celled microscopic organisms and viruses, which are microscopic
but not cellular.
What is microbiology all about?
Microbiology is about cells and how they work, especially the bacteria, a large group
of cells of enormous basic and practical importance (Figure 1.1).
Figure 1.1 Microorganisms. (a, b) A single microbial cell can have an independent
existence. Shown are photomicrographs of phototrophic (photosynthetic) microorganisms
called (a) purple bacteria and (b) cyanobacteriaand (d) bioluminescent (light-emitting) cells of
the bacterium Photobacterium leiognathi grown in laboratory culture. One milliliter of water
from the lake (c) or one colony from the plate (d) contains more than 1 billion (109) individual
cells.
Microbiology is about diversity and evolution, about how different kinds of
microorganisms arose and why.
It is about what microorganisms do in the world at large, in soils and waters, in the
human body, and in animals and plants.
One way or another, microorganisms affect all other life forms on Earth, and thus we
may think of microbiology as the foundation of the biological sciences.
Microorganisms differ from the cells of macroorganisms. The cells of
macroorganisms such as plants and animals are unable to live alone in nature and exist
only as parts of multicellular structures, such as the organ systems of animals or the
leaves of leafy plants.
2
, By contrast, most microorganisms can carry out their life processes of growth, energy
generation, and reproduction independently of other cells.
1. INTRODUCTION TO MICROBIOLOGY
1.1 Microbiology
The science of microbiology revolves around two themes:
(1) Understanding basic life processes, and
As a basic biological science, microbiology uses and develops tools for probing the
fundamental processes of life .
Scientists have been able to gain a sophisticated understanding of the chemical and
physical basis of life from studies of microorganisms because microbial cells share many
characteristics with cells of multicellular organisms; indeed, all cells have much in
common .
Moreover, microbial cells can grow to extremely high densities in laboratory culture,
making them readily amenable to biochemical and genetic study .
These features make microorganisms excellent models for understanding cellular
processes in multicellular organisms, including humans
(2) Applying our understanding of microbiology for the benefit of humankind.
As an applied biological science, microbiology deals with many important practical problems
in medicine, agriculture, and industry For example:
Most animal and plant diseases are caused by microorganisms .
Microorganisms play major roles as agents of soil fertility and in supporting domestic
animal production .
3
, Many large-scale industrial processes, such as the production of antibiotics and human
proteins, rely heavily on microorganisms. Thus both the detrimental and the beneficial
aspects of microorganisms affect the everyday lives of humans.
The Importance of Microorganisms
In this book we will see that microorganisms play central roles in both human
activities and the web of life on Earth.
Although microorganisms are the smallest forms of life, collectively they constitute
the largest mass of living material on Earth and carry out many chemical processes
necessary for other organisms.
In the absence of microorganisms, other life forms would never have arisen and could
not now be sustained. Indeed, the very oxygen we breathe is the result of past microbial
activity (Figure 1.1b).
Moreover, we will see how humans, plants, and animals are intimately tied to
microbial activities for the recycling of key nutrients and for degrading organic matter.
No other life forms are as important as microorganisms for the support and maintenance
of life on Earth.
Microorganisms existed on Earth for billions of years before plants and animals
appeared, and we will see in later chapters that the diversity of microbial life far exceeds
that of the plants and animals.
This huge diversity accounts for some of the spectacular properties of
microorganisms. For example, we will see how microorganisms can live in places
unsuitable for other organisms and how the diverse physiological capacities of
microorganisms rank them as Earth’s premier chemists.
4
