Chp. 1 - Evolution of Microbiology

Microorganisms are also called

Microbes

Acellular

No cell membrane or cells

• ex: viruses, viroids, satellites, prions

Cellular

Has cell membrane and cells

• ex: fungi, protists, bacteria, archaea

What is the importance of microbes?

Populous and diverse, found everywhere, help recycle essential elements, source of nutrients, benefit society - necessary for human survival and food production, some cause disease (very few)

Why are microorganisms the foundation of life on Earth?

Produced much of Earth's oxygen through photosynthesis, first life forms and drive nutrient cycling, enabled major evolutionary events (ex: mitochondria)

What are the essential elements necessary to life?

CHONPS

What is limited in nature, so microbes recycle so that we can reuse?

CHONPS

What are relatively simple in their construction and lack highly differentiated cells and distinct tissues?

Microbes

What must all LIVING organisms have?

A cell membrane, can replicate by themselves

Why are acellular organisms nonliving?

No cell membrane and can't replicate by themselves

What are the cellular microorganisms?

Fungi, protists, bacteria, and archaea

What are the eukaryotic groups?

Fungi and protists

What are the prokaryotic groups?

Bacteria and archaea

Example of fungi

Candida - yeasts, molds

Example of protists

Algae, protozoa, slime molds

Example of bacteria

Escherichia coli

Is Escherichia coli gram + or gram - and how is it shaped?

Gram - and rod shaped

What color does gram - stain?

Red

What color does gram + stain?

Purple

Example of archaea

Methanogens - can make methane gas

What are acellular microorganisms?

Viruses, viroids, satellites, and prions

Do humans, bacteria, and archaea have DNA or RNA and why?

Both bc living organisms

What are satellites composed of?

nucleic acid enclosed in a protein shell

What are satellites?

Virus's lazy cousin - not autonomous, cannot infect alone, need virus to help them

What are the two types of microbial cells?

eukaryotic and prokaryotic

Prokaryotic cells

No nucleus, no organelles

Where is the DNA of prokaryotes located?

Cytoplasm

Transcription

DNA --> RNA

Translation

mRNA --> protein

Where does transcription take place in prokaryotic cells?

Cytoplasm

Where does translation take place in prokaryotic cells?

Cytoplasm at the same time as transcription

Eukaryotic cells have

Nucleus and organelles

Where is DNA located in eukaryotic cells?

Nucleus

Where does transcription take place in eukaryotes?

Nucleus

Where does translation take place in eukaryotes?

Cytoplasm

What do ribosomes have in them?

Protein and RNA

What did Carl Woese do?

Studied ribosomes, focusing on small-subunit of rRNA. Sequenced and compared rRNA based on size - discovered 2 different prokaryotic populations, so split them into bacteria and archaea and created tree of life

Tree of life

Three domain system based on comparison of small subunit rRNAs genes

What are included in the tree of life?

Eukaryotes, bacteria, and archaea

16S rRNA

Bacteria and archaea

18S rRNA

Eukaryea

Are prokaryotes multicellular or unicellular?

Unicellular

Are eukaryotes multicellular or unicellular?

Can be either

Will the tree of life change again? It was last published in 2016

Yes, we discover more and more as time goes on - we still only know about 1% of the microbes out there

Are acellular infectious agents in the tree of life?

No because no living

What are viruses composed of?

Protein coat and nucleic acid (DNA OR RNA - not both)

What are viroids and virusoids composed of?

Single stranded circular RNA, NO protein coat

What are viroids?

Molecules that cause disease in plants

What are prions composed of?

Proteins (amino acids) with secondary and tertiary structure

What is prion disease?

A misfolded protein that can cause other normal proteins to misfold, leading to destruction of cells/neurons

Mad Cow Disease

Bad form of prions are present and cow brain becomes mush

Good form of prions

Neurons need it

Bacteriophages

Infect bacteria

What is the RNA World Hypothesis?

Believed that the world started with RNA and then DNA evolved from it

What provides evidence for the RNA World Hypothesis?

RNA can store information and catalyze reactions (ribozymes, self-splicing/replicating RNA); rRNA is essential for protein synthesis; RNA regulates genes (e.g., gene silencing); ATP is a ribonucleotide—showing cellular energy chemistry is RNA-based.

How does RNA regulate gene expression?

RNAi --> siRNA and miRNA

What makes something RNA?

Presence of hydroxyl (-OH) group on C2

What makes something DNA?

Missing hydroxyl group, so just has (-H) on C2

LUCA

last universal common ancestor

What revealed the major evolutionary split between Bacteria, Archaea, and Eukarya?

rRNA gene sequencing

What does the universal phylogenetic tree determine?

Relatedness

What evolved independently of bacteria?

Archaea and Eukarya

What diverged from common ancestry?

Archaea and Eukarya

What node did archaea diverge from?

The same as eukaryea, so has some similarities to euk and bacteria

Where do archaea form?

Extreme environments

The first cells on Earth were

prokaryotic and anaerobic.

Eukaryotes evolved through

a process involving endosymbiosis between primitive cells

What is the endosymbiotic hypothesis?

Larger primitive cells engulfed smaller prokaryotes, leading to the formation of mitochondria and chloroplasts inside early eukaryotic cells.

What was engulfed during endosymbiosis, and why?

A gram - prokaryote that produced useful products like ATP.

What is genome reduction in endosymbiosis?

Over time, the endosymbiont lost many genes as it became dependent on the host.

Which organelles evolved via endosymbiosis?

Mitochondria and chloroplasts

Which statements support the Endosymbiosis Theory?

Mitochondria and chloroplasts divide independently of the cell using binary fission, both organelles have double membranes, suggesting an engulfment event, both have ribosomes similar to those found in bacteria, and both have their own circular DNA.

Mitochondria originated from what type of organism?

An aerobic Gram-negative α-proteobacterium.

Chloroplasts originated from what type of organism?

Cyanobacteria

What were cyanobacteria originally called, and why?

"Blue-green algae" because they perform photosynthesis, so scientists thought it was an algae

Why is that "blue-green algae" the incorrect name for them?

Cyanobacteria are prokaryotes, not eukaryotic algae.

Why are cyanobacteria important evolutionarily?

They were one of the first times scientists realized bacteria can do photosynthesis

Which eukaryotes contain both mitochondria and chloroplasts?

Plants and algae

How many membranes do Gram-negative bacteria have?

Two (inner cell membrane + outer membrane)

How many membranes do Gram-positive bacteria have?

One

What ribosome size do prokaryotes have?

70S (50S + 30S)

What ribosome size do eukaryotic cytoplasm have?

80S (60S + 40S)

What ribosome size do mitochondria have?

70S because it came from bacteria

What mechanisms induce evolution in prokaryotes?

Horizontal gene transfer and mutation of genetic material

How do bacteria and archaea increase the genetic pool?

Horizontal gene transfer (HGT)

prokaryotes can only replicate

asexually (HGT)

Sexual reproduction

Little bit from each parent

Asexual reproduction

Horizontal gene transfer

Horizontal gene transfer

Information shared from one cell to another (not coming together like in sexual)

Horizontal gene transfer events

Conjugation (cell touches another and open passage between cells + shares DNA), competence (take DNA from environment if cell dies), and phages (virus infects bacteria + takes info from it when it kills it + donate to diff bacteria)

Strains

Descendents from a single, pure microbial culture - same genus + species with slight modifications

Species

Collection of strains

Different types of strains

Biovars, morphovars, and serovars

Biovars

Strains that differ biochemically and physiologically

Morphovars

Differ morphologically (shapes)

Serovars

Differ in antigenic properties (diff antibodies bind to different antigens)

Type strain

The first strain identified/studied

How do you discover new strains?

Sequence to see if it's different

Taxonomy

Science of biological classification

Classification

Arrangement of organisms into groups (taxa)