EXAM ON ORGANISMIC BIO QUESTIONS AND ANSWERS
#10
Microbial universe: - correct answer Estimated 10^11 stars in our galaxy
Microbial universe:
1 kg of soil contains 10^13 bacterial/archaeal cells Vast majority (99%) of these are
unknown - taxonomically or functionally
Wherever they are, bacteria are in great numbers. For example, in humans, eukaryote
cells are outnumbered at least 1 to 10 by bacterial cells.
The 10x greater abundance of bacterial cells in human body lead to the concept of
human microbiome. Medical applications or consequences of human microbiome?
Microbial dark matter - correct answer Rinke et al. (2013) used single-cell sequencing of
201 unculturable (archae-)bacteria from nine environments.
• They assembled genomes from 16S identified unique, previously poorly characterized
and unculturable taxa
Genome and 16S sequence data used to assign into taxa - some of which contained
only unculturable bacteria.
• Based on these data they were able to assign metabolic attributes to previously
unknown bacteria.
• Point: how little we know about bacteria in general
How many genomes in a animal cell? A. One like in every other eukaryote B. Two - one
from poppa, one from momma C. Two as a result of past acquisitions D. This is a silly
question; there are no g-nomes. - correct answer c eukaryotic genome and organelle
genomes
How many bacterial species are there? A. 5,000 B. 50,000 C. 500,000 D. 5,000,000 E.
A and C, although nobody knows for sure. - correct answer E
Features of Domains Bacteria and Archaea A quick review - correct answer • All
prokaryotic cells have
- Nucleoid, no nucleus or nuclear envelopes
- Circular DNA roughly organized into a nucleoid plus plasmids
- No membrane-bound organelles (plastids, mitochondria, golgi, endoplasmic reticulum)
- Bacteria can be unicellular, multicellular or BOTH!
Features of bacteria - correct answer • Nutrition: - Primarily by absorption of food
solutes through cell wall - Perform a wide array chemical reactions including
photosynthesis
• Reproduction predominately asexual, by fission. - Fission - No mitosis, DNA strand
duplicates and is distributed to new cells.
• No sexual reproduction - Genetic recombination facilitated by pili or by close contact of
cells. - Bacteria are promiscuous and share genetic elements readily (Lateral/Horizontal
Gene Transfer - L/HGT).
,Bacteria features
Cellular Detail and Reproduction in Bacteria - correct answer • Folded plasma- and
other membranes function like organelles in eukaryotic cells.
• Ribosomes present, but ~half the size of those in eukaryotic cells.
• Many (up to 40) plasmids may be present.
- Plasmids - Small extra- chromosomal circular DNA molecules that replicate
independently
- Plasmid consists of copies of one or few different DNA molecules.
- Transformation of E. Col
• No mitosis, but fission:
- Copies of the duplicated chromosome migrate to opposite ends of cell.
- Perpendicular walls and cell membranes formed in middle of cell.
- The 2 new cells separate and enlarge to original size.
- Fission can happen every 10 - 20 minutes under ideal conditions
• Usually exhaust food supplies and accumulate wastes
Bacteria features
Cellular Detail and Reproduction in Bacteria
• Three Forms of Genetic Sharing: - correct answer • No gametes or zygotes, no
meiosis
• Three Forms of Genetic Sharing:
• Conjugation - DNA transferred from donor cell to recipient cell usually through pilus
(plural: pili).
• Transformation - Living cell acquires DNA fragments released by dead cells (L/HGT).
• Transduction - DNA fragments carried from one cell to another by viruses.
Features of bacteria
Size, Form, and Classification of Bacteria - correct answer • Small: most bacteria <2-3
micrometers in diameter.
• Occur primarily in three forms:
Cocci: Spherical or elliptical
Bacilli Rod-shaped or cylindrical
Spirilli Helix or spiral
Also classified by:
- Presence of sheath around cells, appendages, endospores, pili, or flagella
- Colony color
- Mechanisms of movement, or lack thereof
- Biochemical, physiological characteristics
- Reaction of cell walls to dye
• Gram-negative - peptidoglycan -
• Gram-positive - peptidoglycan +
Domain bacteria - correct answer True bacteria have muramic acid in cell walls. Differ
also from Archaea in cell wall composition, t-RNA structure and metabolism.
• Bacteria can be
- Heterotrophic - Cannot synthesize own food
, » Majority saprobes - Food from nonliving organic matter: Decay and recycle organic
matter in soil
» Some parasites - Depend on living organisms for food
- Autotrophic - Synthesize organic compounds from simple inorganic substances
» Photosynthetic (oxidative phosphorylation)
» Chemotrophic (redox reactions)
Bacteria possess their genetic material in... A. Nucleus B. A circular chromosome C.
Extrachromosomal plasmids D. Muramic acids - correct answer B C
Phylum Proteobacteria - correct answer • A major phylum of Gram- bacteria, divided to
several subphyla (alpha-, beta-, gamma-, delta-, etc. Proteobacteria).
• Includes many human pathogens (e.g. Escherichia, Salmonella, Yerzinia)
• If you google "Proteus" - the reason for name Proteobacteria becomes obvious, they
are diverse in shape, form and function.
• Includes some N-fixing members
• We talk about Proteobacteria, as eukaryal mitochondria are thought to be descendants
of alpha-proteobacteria.
Phylum Cyanobacteria - correct answer • Simplest photosynthetic bacteria
- Perform oxygenic photosynthesis
- CO2 + Light -> Sugar + O2
- Aerobic nitrogen fixation
- Multicellular cyanobacteria have specialized O2 free tissues for atmospheric N2
fixation
• Known fossils going back >2.5 BYA
• Oxygenated the atmosphere
- Without cyanobacteria other aerobic organisms would never have existed
• Accumulate lipids:
- Engineer them for biodiesel of tomorrow?
• Cyanobacteria and chloroplasts have a single common ancestor
Escherichia coli is ... A. A bacterium B. Gram negative bacterium C. Human microbiome
bacterium D. Human pathogen E. A model organism - correct answer all of the above
Endosymbiosis theory posits that A. Bacteria live inside eukaryote cells B. Ancestral
eukaryons acquired a bacterium that gave rise to the mitochondrion C. Ancestral
eukaryons acquired a bacterium that gave rise to the chloroplast D. Dingo ate my baby -
correct answer B C
Domain Archaebacteria - correct answer • Archaea are autotrophic and heterotrophic
prokarya distinct from Eubacteria - the prefix suggests them as oldest organisms on
Earth (probably not true).
• Archaea classification is difficult - few grow in the laboratory and most only observed
by DNA analysis from environment.
, • Although similar to bacteria in size and shape, archaea possess genes and metabolic
pathways more similar to eukaryotes (e.g. Enzymes for DNA->RNA transcription and
DNA->aa/protein translation).
• Archaea differ from bacteria in cell membranes (ether-linked vs. Ester-linked lipids)
and have alosaminuronic acid in cell wall vs. Muramic acid.
Antibiotics usually do not work on archaebacteria
Domain Archaea - Extremophiles - correct answer • Although present in terrestrial,
aquatic and marine environments - like bacteria, some Archaea can exploit some tough
places to live.
• Examples include hydrothermal vents and hot springs that preclude most othe living
organisms.
• Example - Archaeal Methanogens
- Killed by oxygen - obligate anaerobics
• Energy derived from generation of methane gas (CH4) from carbon dioxide (CO2)
and hydrogen (H2).
Domain Archaea - Extreme Environments - correct answer • Human relevance of the
Archaebacteria:
- No known human pathogens - good thing since many are insensitive to antibiotics.
- Methane bacteria produce methane gas as they digest organic wastes in absence of
oxygen.
• While CH4 is a more potent greenhouse gas than CO2, it is high octane and burns
clean (CO2 and H2O).
• Methane may be used to furnish energy for engines, heating and cooking - biofuel
applications.
• Methane produced on large-scale when organic wastes fed into methane digester.
- Leftover sludge makes excellent fertilizer
What distinguishes Archaea and Eubacteria? A. DNA in chromosomes B. Nucleus C.
Plasmids D. Cell wall components. - correct answer d
Both have A
Neither have B
Eukarya share most recent ancestral node with... A. Eubacteria B. All Archeabacteria C.
Some archaebacteria within that domain D. None of the above, Eukarya diverged
endependently. - correct answer c Lokiarchea
Eukaryotic versus Prokaryotic Cells
Also table pic on phone - correct answer • Prokaryotic - Cells lack a nucleus/nuclear
envelope and other sub-cellular organelles
- Domains: Bacteria • Archaea
• Eukaryotic - Cells contain a nucleus/nuclear envelope and mitochondria.
- Plants and animals, among others
- Organelles - Membrane-bound bodies found within eukaryotic cells
• Multicellularity: All domains of life have species that are unicellular and multicellular
#10
Microbial universe: - correct answer Estimated 10^11 stars in our galaxy
Microbial universe:
1 kg of soil contains 10^13 bacterial/archaeal cells Vast majority (99%) of these are
unknown - taxonomically or functionally
Wherever they are, bacteria are in great numbers. For example, in humans, eukaryote
cells are outnumbered at least 1 to 10 by bacterial cells.
The 10x greater abundance of bacterial cells in human body lead to the concept of
human microbiome. Medical applications or consequences of human microbiome?
Microbial dark matter - correct answer Rinke et al. (2013) used single-cell sequencing of
201 unculturable (archae-)bacteria from nine environments.
• They assembled genomes from 16S identified unique, previously poorly characterized
and unculturable taxa
Genome and 16S sequence data used to assign into taxa - some of which contained
only unculturable bacteria.
• Based on these data they were able to assign metabolic attributes to previously
unknown bacteria.
• Point: how little we know about bacteria in general
How many genomes in a animal cell? A. One like in every other eukaryote B. Two - one
from poppa, one from momma C. Two as a result of past acquisitions D. This is a silly
question; there are no g-nomes. - correct answer c eukaryotic genome and organelle
genomes
How many bacterial species are there? A. 5,000 B. 50,000 C. 500,000 D. 5,000,000 E.
A and C, although nobody knows for sure. - correct answer E
Features of Domains Bacteria and Archaea A quick review - correct answer • All
prokaryotic cells have
- Nucleoid, no nucleus or nuclear envelopes
- Circular DNA roughly organized into a nucleoid plus plasmids
- No membrane-bound organelles (plastids, mitochondria, golgi, endoplasmic reticulum)
- Bacteria can be unicellular, multicellular or BOTH!
Features of bacteria - correct answer • Nutrition: - Primarily by absorption of food
solutes through cell wall - Perform a wide array chemical reactions including
photosynthesis
• Reproduction predominately asexual, by fission. - Fission - No mitosis, DNA strand
duplicates and is distributed to new cells.
• No sexual reproduction - Genetic recombination facilitated by pili or by close contact of
cells. - Bacteria are promiscuous and share genetic elements readily (Lateral/Horizontal
Gene Transfer - L/HGT).
,Bacteria features
Cellular Detail and Reproduction in Bacteria - correct answer • Folded plasma- and
other membranes function like organelles in eukaryotic cells.
• Ribosomes present, but ~half the size of those in eukaryotic cells.
• Many (up to 40) plasmids may be present.
- Plasmids - Small extra- chromosomal circular DNA molecules that replicate
independently
- Plasmid consists of copies of one or few different DNA molecules.
- Transformation of E. Col
• No mitosis, but fission:
- Copies of the duplicated chromosome migrate to opposite ends of cell.
- Perpendicular walls and cell membranes formed in middle of cell.
- The 2 new cells separate and enlarge to original size.
- Fission can happen every 10 - 20 minutes under ideal conditions
• Usually exhaust food supplies and accumulate wastes
Bacteria features
Cellular Detail and Reproduction in Bacteria
• Three Forms of Genetic Sharing: - correct answer • No gametes or zygotes, no
meiosis
• Three Forms of Genetic Sharing:
• Conjugation - DNA transferred from donor cell to recipient cell usually through pilus
(plural: pili).
• Transformation - Living cell acquires DNA fragments released by dead cells (L/HGT).
• Transduction - DNA fragments carried from one cell to another by viruses.
Features of bacteria
Size, Form, and Classification of Bacteria - correct answer • Small: most bacteria <2-3
micrometers in diameter.
• Occur primarily in three forms:
Cocci: Spherical or elliptical
Bacilli Rod-shaped or cylindrical
Spirilli Helix or spiral
Also classified by:
- Presence of sheath around cells, appendages, endospores, pili, or flagella
- Colony color
- Mechanisms of movement, or lack thereof
- Biochemical, physiological characteristics
- Reaction of cell walls to dye
• Gram-negative - peptidoglycan -
• Gram-positive - peptidoglycan +
Domain bacteria - correct answer True bacteria have muramic acid in cell walls. Differ
also from Archaea in cell wall composition, t-RNA structure and metabolism.
• Bacteria can be
- Heterotrophic - Cannot synthesize own food
, » Majority saprobes - Food from nonliving organic matter: Decay and recycle organic
matter in soil
» Some parasites - Depend on living organisms for food
- Autotrophic - Synthesize organic compounds from simple inorganic substances
» Photosynthetic (oxidative phosphorylation)
» Chemotrophic (redox reactions)
Bacteria possess their genetic material in... A. Nucleus B. A circular chromosome C.
Extrachromosomal plasmids D. Muramic acids - correct answer B C
Phylum Proteobacteria - correct answer • A major phylum of Gram- bacteria, divided to
several subphyla (alpha-, beta-, gamma-, delta-, etc. Proteobacteria).
• Includes many human pathogens (e.g. Escherichia, Salmonella, Yerzinia)
• If you google "Proteus" - the reason for name Proteobacteria becomes obvious, they
are diverse in shape, form and function.
• Includes some N-fixing members
• We talk about Proteobacteria, as eukaryal mitochondria are thought to be descendants
of alpha-proteobacteria.
Phylum Cyanobacteria - correct answer • Simplest photosynthetic bacteria
- Perform oxygenic photosynthesis
- CO2 + Light -> Sugar + O2
- Aerobic nitrogen fixation
- Multicellular cyanobacteria have specialized O2 free tissues for atmospheric N2
fixation
• Known fossils going back >2.5 BYA
• Oxygenated the atmosphere
- Without cyanobacteria other aerobic organisms would never have existed
• Accumulate lipids:
- Engineer them for biodiesel of tomorrow?
• Cyanobacteria and chloroplasts have a single common ancestor
Escherichia coli is ... A. A bacterium B. Gram negative bacterium C. Human microbiome
bacterium D. Human pathogen E. A model organism - correct answer all of the above
Endosymbiosis theory posits that A. Bacteria live inside eukaryote cells B. Ancestral
eukaryons acquired a bacterium that gave rise to the mitochondrion C. Ancestral
eukaryons acquired a bacterium that gave rise to the chloroplast D. Dingo ate my baby -
correct answer B C
Domain Archaebacteria - correct answer • Archaea are autotrophic and heterotrophic
prokarya distinct from Eubacteria - the prefix suggests them as oldest organisms on
Earth (probably not true).
• Archaea classification is difficult - few grow in the laboratory and most only observed
by DNA analysis from environment.
, • Although similar to bacteria in size and shape, archaea possess genes and metabolic
pathways more similar to eukaryotes (e.g. Enzymes for DNA->RNA transcription and
DNA->aa/protein translation).
• Archaea differ from bacteria in cell membranes (ether-linked vs. Ester-linked lipids)
and have alosaminuronic acid in cell wall vs. Muramic acid.
Antibiotics usually do not work on archaebacteria
Domain Archaea - Extremophiles - correct answer • Although present in terrestrial,
aquatic and marine environments - like bacteria, some Archaea can exploit some tough
places to live.
• Examples include hydrothermal vents and hot springs that preclude most othe living
organisms.
• Example - Archaeal Methanogens
- Killed by oxygen - obligate anaerobics
• Energy derived from generation of methane gas (CH4) from carbon dioxide (CO2)
and hydrogen (H2).
Domain Archaea - Extreme Environments - correct answer • Human relevance of the
Archaebacteria:
- No known human pathogens - good thing since many are insensitive to antibiotics.
- Methane bacteria produce methane gas as they digest organic wastes in absence of
oxygen.
• While CH4 is a more potent greenhouse gas than CO2, it is high octane and burns
clean (CO2 and H2O).
• Methane may be used to furnish energy for engines, heating and cooking - biofuel
applications.
• Methane produced on large-scale when organic wastes fed into methane digester.
- Leftover sludge makes excellent fertilizer
What distinguishes Archaea and Eubacteria? A. DNA in chromosomes B. Nucleus C.
Plasmids D. Cell wall components. - correct answer d
Both have A
Neither have B
Eukarya share most recent ancestral node with... A. Eubacteria B. All Archeabacteria C.
Some archaebacteria within that domain D. None of the above, Eukarya diverged
endependently. - correct answer c Lokiarchea
Eukaryotic versus Prokaryotic Cells
Also table pic on phone - correct answer • Prokaryotic - Cells lack a nucleus/nuclear
envelope and other sub-cellular organelles
- Domains: Bacteria • Archaea
• Eukaryotic - Cells contain a nucleus/nuclear envelope and mitochondria.
- Plants and animals, among others
- Organelles - Membrane-bound bodies found within eukaryotic cells
• Multicellularity: All domains of life have species that are unicellular and multicellular
