Microbiology

Question 1

What are the 2 themes in microbiology?

Answer 1

1. Understanding basic life processes

•Microbes are excellent models for understanding cellular processes in unicellular and multicellular organisms

2. Applying that knowledge to the benefit of humans

•Microbes play important roles in medicine, agriculture, and industry

Question 2

What is the importance of microorganisms?

Answer 2

• Oldest form of life
• Largest mass of living material on Earth
• Carry out major processes for biogeochemical cycles
• Can live in places unsuitable for other organisms
• Other life forms require microbes to survive

Question 3

What is a cell?

Answer 3

A dynamic entity that forms the fundamental unit of life

Question 4

Name the 4 elements of a microbial structure

Answer 4

•Cytoplasmic (cell) membrane
Barrier that separates the inside of the cell from the outside environment

•Cytoplasm
Aqueous mixture of macromolecules, ions, and ribosome

•Ribosomes
Protein-synthesizing structures

Cell wall
Present in most microbes; confers structural strength

Question 5

Name a few differences between Eukaryotes and Prokaryotes

Answer 5

•Prokaryotes

• No membrane-enclosed organelles, no nucleus
• Generally smaller than eukaryotic cells

•Eukaryotes

• DNA enclosed in a membrane-bound nucleus
• Cells are generally larger and more complex
• Contain organelles

Question 6

Define genome and describe DNA in Eukaryotes

Answer 6

•Genome

•A cell’s full complement of genes

•Eukaryotic DNA is linear and found within the nucleus

• Associated with proteins that help in folding of the DNA
• Usually more than one chromosome
• Typically two copies of each chromosome
• During cell division, nucleus divides by mitosis
• During sexual reproduction, the genome is halved by meiosis

Question 7

Describe the DNA of prokaryotes

Answer 7

• Prokaryotic cells generally have a single, circular DNA molecule called a chromosome
• DNA aggregates to form the nucleoid region (Figure 1.2a)
• Prokaryotes also may have small amounts of extrachromosomal DNA called plasmids that confer special properties (e.g., antibiotic resistance)

Question 8

What is the difference between a Escherichia coli genome and a human cell?

Answer 8

• Escherichia coli genome
• 4.64 million base pairs
• 4,300 genes
• Human cell
• 1,000✕ more DNA per cell than E. coli
• 7✕ more genes than E. coli

Question 9

What are the 6 characteristics of living cells?

Answer 9

• Metabolism: chemical transformation of nutrients
• Reproduction: generation of two cells from one
• Differentiation: synthesis of new substances or structures that modify the cell (only in some microbes)
• Communication: generation of, and response to, chemical signals (only in some microbes)
• Movement: via self-propulsion, many forms in microbes
• Evolution: genetic changes in cells that are transferred to offspring

Question 10

What drives evolution?

Name some things that ALL cell have and SOME cells have

Answer 10

1. Variation

2.

Question 11

How do cells carry out chemical reactions?

Answer 11

•Enzymes: protein catalysts of the cell that accelerate chemical reactions

• Cells store and process information that is eventually passed on to offspring during reproduction through DNA (deoxyribonucleic acid) and evolution
• Transcription: DNA produces RNA

•Translation: RNA makes protein

Question 12

What can cell growth be defined as? (Think of the big picture)

Answer 12

•The link between cells as machines and cells as coding devices

Question 13

What were the first cells? (Trick Question)

Answer 13

• First self-replicating entities may not have been cells
• Last universal common ancestor (LUCA): common ancestral cell from which all cells descended

Question 14

How old is the Earth?

When did the first cells come about?

How long was the world anoxic?

When was the world microbial?

Answer 14

Earth is 4.6 billion years old

•First cells appeared between 3.8 and 3.9 billion years ago

•The atmosphere was anoxic until ~2 billion years ago

• Metabolisms were exclusively anaerobic until evolution of oxygen-producing phototrophs
• Life was exclusively microbial until ~1 billion years ago

Question 15

What are the similarities between Archaea and Prokaryotes?

Answer 15

Achaea are a prokaryote. The have similarity in structures and functions.

Question 16

What are the differences between Evolution and a Phylogeny?

Answer 16

•Evolution

•The process of change over time that results in new varieties and species of organisms

•Phylogeny

• Evolutionary relationships between organisms
• Relationships can be deduced by comparing genetic information in the different specimens (Figure 1.6a)
• Ribosomal RNA (rRNA) is excellent for determining phylogeny
• Relationships visualized on a phylogenetic tree

Question 17

What are the three distinct lineages of cells called domains?

Are Archaea and Bacteria related?

Answer 17

• Bacteria (prokaryotic)
• Archaea (prokaryotic)

Eukarya (eukaryotic

NO not related

Question 18

What 2 domains did LUCA introduce?

What 2 domains did Archaea form?

Answer 18

•From the last universal common ancestor (LUCA), evolution proceeded to form two domains

• Bacteria
• Archaea

•Archaea later diverged to form two domains

• Archaea
• Eukarya

Question 19

Define the following: microbial communities, habitat, ecosystem, microbial ecology

Answer 19

• Microorganisms exist in nature in populations of interacting assemblages called microbial communities (Figure 1.7)
• The environment in which a microbial population lives is its habitat
• Ecosystem refers to all living organisms plus physical and chemical constituents of their environment
• Microbial ecology is the study of microbes in their natural environment

Question 20

How is diversity and abundances of microbes are controlled?

Answer 20

• Diversity and abundances of microbes are controlled by resources (nutrients) and environmental conditions (e.g., temp, pH, O2)
• The activities of microbial communities can affect the chemical and physical properties of their habitats

Question 21

What environments are microbes found?

Answer 21

• Microbes are found in almost every environment imaginable
• Extremophiles are Bacteria and Archaea that can grow in extremely harsh environments
• Very hot or very cold
• Very acidic or very caustic
• Very salty or very osmotically stressing
• Very high pressure

Question 22

Where are microbial cells found?

Answer 22

• Global estimate is 5 ✕ 1030 cells
• Most microbial cells are found in oceanic and terrestrial subsurfaces
• Microbial biomass is significant, and cells are key reservoirs of essential nutrients (e.g., C, P, N)

Question 23

What sickness is caused my microbial organisms?

Answer 23

Pnemonia

Question 24

What are the positive and negaive impacts of using microbials in Agriculture?

Answer 24

•Positive impacts

• Nitrogen-fixing bacteria
• Cellulose-degrading microbes in the rumen
• Regeneration of nutrients in soil and water

•Negative impacts

•Diseases in plants and animals

Question 25

What do Rhigobium bacteria require? What is Lehemoglobin?

Answer 25

Rhigobium bacteria require nitrogen and anaerobic conditions. Oxygen scavengers.

Question 26

In the body where are there high numbers of microorganisms?

Answer 26

* Colon and oral cavity * Positive impacts * Synthesize vitamins and other nutrients * Compete with pathogens for space and resources

Question 27

How is the intestinal tract selective?

Answer 27

The intestinal tract has variable pH's

Question 28

What are the positive and negative impacts of having micribials in food?

Answer 28

* Microorganisms and food * Negative impacts * Microorganisms can cause food spoilage; for many foods, methods of preservation are needed * Positive impacts (Figure 1.11) * Microbial transformations (typically fermentations) yield * Dairy products (e.g., cheeses, yogurt, buttermilk) * Other food products (e.g., sauerkraut, pickles, leavened breads, beer)