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Biology Notes, Brock Microbiology, chapter 1 notes
Microbiology (BIO 340)
University of Phoenix
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Biology/340 Notes
Microorganisms are everywhere, their activities have tremendous impacts on everything in our biosphere. The composition of your microbiome changes in response to your diet, genes, health and medications you take.
Chapter One
1 Microbes
Microorganisms (also called microbes) are lifeforms too small to be seen by the unaided eye. (on earth for billions of years prior to plant and animal life)
in every environment on earth diverse in form and function
Many microbes are undifferentiated single-celled organisms, but some can form complex structures, and some are even multicellular.
Microbes typically live in complex microbial communities (their activity is regulated by their interactions with each other and their environment). Microbes represent a large fraction of earth’s biomass.
Oxygen (O2) we breath is the result of microbial activity
Pathogen- microbe that causes disease
Microbes are woven into human life as well, from infectious disease food we eat, health of our animals, and fuel.
Microbiology- is the study of the dominant form of life on earth, the effect that microbes have on our planet. (Born of the microscope)
Microbial Culture- Collection of cells grown in or on a nutrient medium.
Medium- (Plural, media) is a liquid or solid nutrient mixture containing the nutrients for a microbe to grow.
Growth- To refer to the increase in cell number as a result of cell division.
A.) A single microbial cell on a solid nutrient medium can grow and divide into millions of cells that for a visible colony.
Colony- A macroscopically visible population of cells growing from a single cell.
A.) Visible colonies make it easier to see and grow microbes B.) Comprehension of the microbial basis of disease and microbial biochemical diversity has relied on the ability to grow microbes in a laboratory.
**Bioluminescent (Light emitting) **
**A single colony can contain more than 10 million (10^7) individual cells. **
Microbes have the ability to grow rapidly under controlled conditions which makes them highly useful for experiments about life processes.
Most discoveries about molecular and biochemical life have been made using microbes.
** The study of molecules and their interactions are essential in defining the working of microbial cells, and the tools of molecular biology and biochemistry are foundational to microbiology **.
**Molecular biology has provided a variety of ways to study microbes without the need for their cultivation in a lab **.
**The tools of genomics and molecular genetics have allowed microbiologists to study the genetic basis of life, how genes evolve and how they regulate the activities of cells **.
Quiz 1. In what ways are microbes important to humans? 2. Why are microbial cells useful for understanding the basis of life? 3. What is a microbial colony and how is one formed?
Examination of cell structure reveals TWO major structural classes of cells, called Prokaryotic and Eukaryotic.
Eukaryotic- are found in the phylogenetic domain Eukarya. Which includes plants and animals as well as diverse microbial eukaryotes such as (algae, protozoa, and fungi).
These cells contain an assortment of membrane-enclosed cytoplasmic structures called organelles. These include the DNA-containing nucleus but also the mitochondria and chloroplasts , organelles that specialize in energy and various other organelles.
Prokaryotic- are found in the domains Bacteria and Archaea. Prokaryotic cells have few have few internal structures, they lack a nucleus , and they typically lack organelles (1). The prokaryotic cell structure evolved prior to the evolution of the eukaryotic cell. Archaea and Bacteria both contain exclusively prokaryotic cells, these groups have diverged greatly but Archaea share many molecular and genetic characteristics with cells of Eukarya.
Genes, Genomes, Nucleus, and Nucleoid
Other than cytoplasmic membrane and ribosomes, all cells also possess a DNA genome. The genome is the complement of all genes in a cell. The genome is the living blueprint of an organism; the characteristics, activities, and very survival of a
cell are governed by its genome. A gene is a segment of DNA that encodes a protein or an RNA molecule.
The genomes of prokaryotic cells and eukaryotic cells are organized differently.
Eukaryotes, DNA is present as several linear molecules within the membrane-enclosed nucleus, a structure in eukaryotic cells that contains the cell’s DNA genome. Eukaryotic cells are usually much larger and less compact than Prokaryotic cells.
Prokaryotes, are typically closed circular chromosomes (few prokaryotes have linear chromosomes). The chromosome aggregates within the prokaryotic cell to form the nucleoid, (an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material.) A mass visible in the electron microscope. Most prokaryotic cells have only a single chromosome, but many also contain one or more DNA distinct from that of chromosome, called plasmids, an extra chromosomal genetic element NOT essential for growth, but confer some special property on the cell (unique metabolism, or antibiotic resistance). Genomes of Bacteria and Archaea are typically small and compact and most contain between 500 and 10,000 genes encoded by .5 to 10 million base pairs.
A human cell contains approximately 3 billion base pairs, which encode about 20,000-25,000 genes.
Activities of Microbial Cells
In nature microbial cells typically live in groups call microbial communities (1). Figure (1) is some of the ongoing cellular activities within that microbial community. All shells show some form of Metabolism, all biochemical reactions in a cell, by taking up nutrients from the environment and transforming them into new cell materials and waste products. During which, energy is conserved to support synthesis of new structures. Production of these new structures culminates, reaches its highest point, in the division of the cell to form two cells. Microbial growth results from successive rounds of cell division.
Microbial growth requires replication of the genome though the process of DNA replication, followed by cell division. All cells carry out the process of transcription, translation, and DNA replication.
Many microbial cells are capable of motility , a change of position that does not change location, typically by self-propulsion (1). It allows cells to relocate in response to environmental conditions. Some cells undergo differentiation, the structural adaptation of some body part for a particular function, which may result in the formation of modified cells for growth, dispersal, or survival. Cells also respond to chemical signals in their environment, from other cells of either different or the same species, and they can often trigger new cellular activities.
Microbial cells therefore exhibit intercellular communication, they are “aware” of their neighbors and can respond accordingly.
Many prokaryotic cells can also exchange genes with neighboring cells, either of the same or different species, in the process of horizontal gene transfer.
Evolution, sequence of events involved in evolutionary development, results when genes in a population of cells change in sequence and frequency over time, leading to descent with modification. Evolution of microbes can be very rapid relative to that of plants and animals.
For example, the indiscriminate use of antibiotics in human and veterinary medicine has selected for the proliferation rapid increase, of antibiotic resistance in pathogenic bacteria.
Quiz 1. What structures are universal to all types of cells? 2. What processes are universal to all types of cells? 3. What structures can be used to distinguish between prokaryote and eukaryote cells?
1 Microbes and the Biosphere
Microbes are the oldest form of life on earth, and they have evolved to perform critical functions that sustain the biosphere.
Earth is about 4 billion years old, microbial cells first appeared between 3 and 4 billion years ago (Figure 1). During the first 2 billion years earth’s atmosphere was axonic , Oxygen was absent, and only nitrogen, carbon dioxide and a few other gases were present. Only microbes capable of anaerobic metabolisms (metabolisms not requiring oxygen) could survive.
Biology Notes, Brock Microbiology, chapter 1 notes
Course: Microbiology (BIO 340)
University: University of Phoenix
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