Download Viruses, Bacteria, Archaea, and Protists

Viruses, Bacteria, Archaea, and Protists
The Diversity of Life 1
Amazing Living Things
• Record Holders.
– Biggest: 27m Blue Whale, 100m redwood tree, sea kelp
274m, 1,500 acre fungus.
– Deepest: 3km bacteria; Highest: 12 species of bacteria in
Himalayas.
– Hottest: Archaean Pyrolobus fumarii lives at 113°C; Coldest:
bacterium Phormidium frigidum freezing water.
– Oldest: Sequoia 3,500; Bristlecone Pine 4,900; Bacterial
spores in amber 25-40 Mya, or archaen spores in salt
crystals from 250 Mya.
Amazing Living Things
• Importance of Microbes.
– All living things classified in three domains:
Bacteria, and Archae, or Eukarya
– Microbes indispensable to life: produce half of
Earth’s O2, nitrogen fixation, decomposition, and
over half of Earth’s biomass. More bacterial than
human cells in your body
Viruses: Making a Living by Hijacking Cells
• Viruses are not regarded as living organisms; lack some
attributes of life.
– Are infectious particles, incapable of replicating
independently.
– Lack cellular organization and metabolism.
– Consist of RNA or DNA usually enclosed in protein coat
(viroids
viroids lack protein coat).
Viruses: Making a Living by Hijacking Cells
• Invade host cell and direct its genetic machinery to churn out
multiple copies of virus.
• Most viruses composed of three large-scale structures.
– Genetic material in its core (DNA or as in HIV two strands of
RNA)
– Capsid protein coat.
– Fatty membrane envelope with spike-like proteins on the
surface that enable binding to target host cell.
Viruses: Making a Living by Hijacking Cells
• Invading the host cell.
– Life Cycle: Binding and fusion with target host T-cell
followed by reverse transcriptase creating DNA copy of viral
RNA and then integrase allows integration of viral DNA into
host chromosome. May remain dormant but can be triggered
to enter replication phase.
Viruses: Making a Living by Hijacking Cells
• Invading the host cell.
– Here the viral genetic material directs synthesis of more
copies of itself and protein coat; these components then
assemble themselves into viral particles; activity of an
enzyme is then triggered, which leads to lysis of host cell
and spread to other uninfected cells.
Viruses: Making a Living by Hijacking Cells
• Viruses infect many organisms, including bacteria (T4 injects
its DNA inside bacteria), and are prevalent (1 ml of sea water
has 10 million viral particles).
Essay: An Unwanted Guest: The Persistence of
Herpes
• 1/5 Americans over 12 infected.
• Caused by Herpes simplex viruses (cause chickenpox,
shingles, and the Epstein-Barr disease).
• Herpes simplex type 1 usually “oral,” type 2 usually
“genital.” But either variety can end up in either
location.
Essay: An Unwanted Guest: The Persistence of
Herpes
• The herpes sores are the result of newly formed virus
particles breaking out and destroying skin cells.
• Lies dormant after initial infection by migrating up
axons to the nucleus inside the cell body.
• Stresses like UV light can trigger re-eruption.
Viruses: Making a Living by Hijacking Cells
• Effects on plants, and animals; cause much agricultural loss,
mild to deadly human diseases (smallpox, chicken pox,
measles, mumps, colds, flu, polio, herpes, rabies, AIDS, some
types of cancer).
Essay: Not Alive, but Deadly: Prions and “Mad
Cow’’ Disease
• Unusual for a transmissible human diseases because its cause
is component part of a living thing –a misshapen version of a
normal protein. Responsible for Creutzfeldt-Jakob disease, and
also Mad Cow disease.
Bacteria: Masters of Every Environment
• Characteristics of bacteria.
– Lack cell nucleus, as do all prokaryotes (eukaryotes have
nucleus).
– No membrane-bound organelles, no cytoskeleton.
– DNA present as single chromosome; haploid organisms.
– Reproduction is asexual, by simple splitting (binary fission);
daughter cells genetic clone of parent cell.
Bacteria: Masters of Every Environment
• Characteristics of bacteria.
– Are single-celled, extremely small. .
Bacteria: Masters of Every Environment
• Characteristics of bacteria.
– Bacteria varied in shapes.
• Cocci—spherical.
Cocci
• Bacilli—rod-shaped.
Bacilli
• Spirochetes—spiral-shaped.
Spirochetes
Bacteria: Masters of Every Environment
• Bacteria exist in staggering numbers in a wide range of
habitats.
– Microflora of human gut includes 600 species of bacteria in
mouth alone; 100 trillion bacteria in digestive tract, equal to
number of cells in human body. 10,000 different species in a
handful of earth, the number of individual bacteria in mouth
probably exceeds number of people ever existed, onequarter of feces by weight consists of bacteria.
Bacteria: Masters of Every Environment
• Bacteria exist in staggering numbers in a wide range of
habitats.
– Nitrogen-fixing bacteria have symbiotic relationship with
some plants—convert molecular nitrogen into forms usable
by plant; nitrogen needed by animals comes ultimately from
plants. We also get various sugars and vitamins for our diet
from resident bacteria.
– Bacteria play an important role as decomposers (as in city
sewage plants).
Bacteria: Masters of Every Environment
• Intimate Strangers: Humans and Bacteria.
– Mutualism: relationship between two organisms that
benefits both.
• Rats with digestive bacteria wiped out require 30% more
calories to maintain body weight, because they have a
lower number of intestinal cells that move nutrients.
• Metabolize sugars we cannot digest and produce some
vitamins.
Bacteria: Masters of Every Environment
• Bacteria and Human Disease.
– Some bacteria are pathogenic, disease-causing:
tuberculosis, syphilis, gonorrhea, cholera, tetanus, botulism,
leprosy, typhoid fever, and diphtheria, food poisonings and
blood-borne infections,bubonic plague, Anthrax (Bacillus
anthracis).
– Damage comes from substances secreted or left behind
(toxins, substances that harmfully alter living tissue or
interfere with biological processes).
Bacteria: Masters of Every Environment
• Bacteria and Human Disease.
– Antibiotics must exploit differences in cell biology
of bacteria and humans to keep from harming
patient (e.g., penicillin destroys bacterial cell walls,
but has no effect on animal cells).
– Threat of antibiotic resistance. Half antibiotics go
to livestock in animal feed as growth stimulants.
Essay: The Discovery of Penicillin
• Antibiotics are used to kill bacteria.
– Originated from fungi.
Essay: Modes of Nutrition
• Autotrophs.
– Photoautotrophy—use light energy and carbon dioxide to
create energy-rich carbon compounds, as do plants, some
bacteria, and many protists.
– Chemoautotrophy—use inorganic compounds (hydrogen
sulfide, ferrous iron) to fix carbon from carbon dioxide.
Some bacteria and archaea.
Essay: Modes of Nutrition
• Heterotrophs.
– Obtain energy from organic material, as do animals and
fungi.
– Photoheterotrophy, uses sunlight for energy, but the carbon
comes from surrounding organic material. Some bacteria
and archaea.
– Chemoheterotrophy, in which organic materials (better
known as food) act as both carbon supplier and energy
source Almost all animals, all fungi, most bacteria, many
protists, and a few plants.
Domain Archaea: From Marginal Player to Center
Stage
• Newly recognized as ancient group of prokaryotes, possibly
ancestral to all life.
– Divergent from all other life-forms; most genes (from
Methanococcus) unique to group, not previously known to
science. Are prevalent; 30 percent of microscopic organisms
living off Antarctica are Archaea.
– Are microscopic, single-celled, lack nuclei.
Domain Archaea: From Marginal Player to Center
Stage
• Some live in extreme environments (extremophiles).
– High or low temperatures, high pressure, high salt,
extreme pH.
– Hard to culture in lab, therefore little known.
– Of great interest to biotechnologists.
Protists: Pioneers in Diversifying Life
• Protista are grab-bag category of eukaryotes, defined
by what they are not
– Are not plants, fungi, or animals.
– Most are single-celled, most in moist or aquatic
habitats.
– Some are photoautotrophic, some are ingestive
heterotrophs, some are capable of both modes of
nutrition.
Protists: Pioneers in Diversifying Life
• Plants evolved from one group of protists (green
algae), animals from another (probably
choanoflagellates), fungi from yet another (probably
chytrid-like Protista).
• Movement powered by flagella, cilia, or pseudopodia.
• Some protists are colonial; may have been a steppingstone toward multicellularity.
Protists: Pioneers in Diversifying Life
• Some protists are multicellular.
– Significance of multicellularity—makes division of
labor among cells possible; greater tissue
complexity.
– Some seaweeds (multicellular) can be enormous—
giant kelps grow 60m in a year.
– 100,000 known species.
Protists: Pioneers in Diversifying Life
• Some protists are multicellular.
– Harmful to humans: Plasmodium falciparum, causes malaria;
intestinal parasite Giardia contaminates water causing
diarrhea if ingested; sleeping sickness, and amoebic
dysentery caused by protists. 1840s Irish Potato Famine
caused by fungus-like protist, Phytophthora infestans. Close
relative, Phytophthora ramorum, is now wiping out stands of
California oak trees and bay laurels.
Protists and Sexual Reproduction
• Most reproduce by cell-splitting, but some evolved sexual
reproduction.
– Ancient, early-evolving protist, single-celled algae
Chlamydomonas usually divides through cell-splitting, but
under nutritional stress two haploid cells fuse to create a
zygote which then undergoes meiosis to create four new
offspring with combinations of the original parental
chromosomes.
– Two mating types (+ and – differ in whip-like flagellar
structures).
Plant-Like Protists
• “Golden” alga, freshwater Synura scenedesmus shows
transition between the single-celled and multicelled
life; Exhibit colonial multicellularity: individual cells
form stable associations with one another but do not
take on specialized roles.
Plant-Like Protists
• Volvox, green algae, has true-multicellularity (individual cells
exist in stable groups, with different cells in a group
specializing in different functions. Colony of 500-60,000 cells
forming a sphere use their flagella to move. Not all cells in
colony reproduce, only select group without flagella. As such,
Phytoplankton are single-celled protists called algae.
Plant-Like Protists
• Brown alga —giants of the protist world (sea kelp 100 meters
long), notable for organized assemblages of cells that conduct
food (leaf-like “blades” and stem-like “stalks”).
• All are phytoplankton: small photosynthetic organisms in
ocean surface, perform much of Earth’s photosynthesis at base
of food web, produce much of its oxygen. Sustain aquatic food
chains—zooplankton eat them, and in turn are eaten by larger
animals and other heterotrophs; some whales feed on plankton
directly.
Animal-Like Protists
• Formerly protozoa), do not obtain nutrients from
photosynthesis, instead from consumption and internal
digestion.
• Paramecium.
– Takes food in through gullet, digests in a food vacuole, and
then empties the resulting waste into the outside world
through an exterior pore. Some species even have tiny dartlike structures (called trichocysts) that they can shoot out
when threatened.
Animal-Like Protists
• Paramecium.
– Ameboid protists use pseudopods, take in food by
endocytosis.
– Examples.
• Entamoeba hystolytica, ~ 100,000 deaths per year, mostly
in the tropics, by entering the human digestive system
through contaminated water (amoebic dysentery).
Animal-Like Protists
• Paramecium.
– Examples.
• Giardia lamblia, reason not to drink stream or lake water
without filtering, boiling, and/or treating it (with iodine or
chlorine). Lives in small intestines of humans and other
animals. Symptoms include nausea, diarrhea, and
vomiting. It gets around by pairs of whip-like flagella like
algae protists.
Fungi-Like Protists
• Fungi obtain nutrients by sending out slender filaments,
releasing digestive enzymes and then absorbing the nutrients.
Fungus-like protists, oomycetes, operate the same way.
• Examples.
– Irish Potato Famine, Phytophthora infestans.
– Water mold (saprobes)
saprobes),
saprobes) organisms that obtain their nutrition
from dead organic matter.
Fungi-Like Protists
• Examples.
– Plasmodial slime mold: several forms during its life-cycle.
Fuses plasma membranes of many cells resulting moving
mass of cytoplasm with multiple nuclei; moving by
“cytoplasmic streaming,” it consumes underlying bacteria,
fungi, and bits of organic material. Like fungi, when nutrition
is scarce, it changes shape, forming a structure that
releases fungus-like spores.
Fungi-Like Protists
• Examples.
– Dictyostelium discoideum, “cellular slime mold” can exist as
individual microscopic cells, but if its bacterial food runs
low, individual cells aggregate and develop into a migrating
“slug” of up to 100,000 cells which can finally arrange into a
stalk-like reproductive structure that releases spores from
its apex.