Transcript MICROBIOLOGY

MICROBIOLOGY - ALCAMO
LECTURE: CRITERIA FOR
PROKARYOTES & EUKARYOTES
Introduction - Cells
• All living organisms have cells
• Basic unit of structure
• Large organisms – many cells
• Cells are organized into:
– Tissues – stomach lining
– Organs – esophagus, stomach, intestines
– Systems – digestive system
MICROORGANISMS
One or a few cells take care of all functions
Prokaryotic Cell:
• No nuclear membrane
• No other internal membranes (no
organelles)
• Only has a cell membrane
• Examples – bacteria, cyanobacteria
.
PROKARYOTES
- They are very small cells
- They have a very thin cell wall:
- Shape
- Protection
- They have a cell membrane:
- Lines the cell wall
- Regulates molecular traffic
- They have a nucleoid or nuclear region
where their one, looped molecule of DNA
resides
PROKARYOTES
- Their cytoplasm is a soup of chemicals
(including free ribosomes), where all cell
activities take place
- They may contain a flagella – a long hairlike appendage made of protein and
responsible for motion in MO’s
- May have one or many
- Made of protein flagellin
- Movement is chemically driven - chemotaxis
Eukaryotic Cell:
•Has a nuclear membrane
•Has other membrane bound organelles:
mitochondria
Golgi bodies
endoplasmic reticulum
•Examples – animals, plants, fungi, protozoa,
unicellular algae
EUKARYOTES
- They are larger cells than the prokaryotes
- They may have a 3 layer cell wall:
- Shape
- Protection
- They have a cell membrane:
- Lines the cell wall
- Regulates molecular traffic
- They have a nucleus with a nuclear membrane:
- Double stranded DNA (chromosomes)
- RNA
.
- They have a cytoplasm – Soup of chemicals
containing membrane bound organelles for
all cell activities
- They may have a flagella –
- cable-like
- Made of tubulin protein
- Arranged in a microtubule array of 9
doublets around 2 singlets
Prokaryotic vs. Eukaryotic Cells
Characteristic
Prokaryotes
Eukaryotes
Nucleus
Absent
Present with nuclear
membrane
Organelles
Absent
Present in a variety of forms
DNA Structure
Single closed loop
Naked strand with no protein
Multiple chromosomes
Protein associated with DNA
Chlorophyll
When present – dissolved in
cytoplasm
When present –contained in
chloroplasts
Ribosomes
Smaller and free in
cytoplasm
Larger and often bound to
membranes
Cell walls
Present and complex
Present /absent and simple
Reproduction
Fission – no mitosis
Mitosis
Examples
Bacteria, Cyanobacteria
Fungi, protozoa, plants,
animals, humans
Classification of Organisms
-Eukaryotes - all multicellular organisms and
unicellular organisms (except 2)
Examples: mammals, fish, plants, fungi,
algae and protozoa
-Prokaryotes – (the other 2) only bacteria and
cyanobacteria
Microorganism Size
• Micrometer – unit of length most
commonly used (1/1,000,000 of a meter)
• MO’s range in size from almost visible
protozoa (100um) down to incredibly small
viruses (0.01 um)
• Most bacteria are 1 – 5 um in length
Bacteria
• Prokaryotes and one of the most abundant
organisms on earth
• Can affect us positively (digest sewage, extract N
from air for plants, break down dead and decaying
matter)
• Can be harmful to us (produce toxins in our
bodies, infect plants and animals, etc)
• Are able to live under almost any conditions
(arctic ice, hot springs, ocean trenches, acidic
conditions, no oxygen)
Small Bacteria
• Rickettsiae barely seen with light
microscope
• Transmitted by arthropods such as ticks and
lice
• Can cause Rocky Mountain spotted fever
and typhus fever
Small Bacteria
• Chlamydiae – even smaller than rickettsiae
and can’t be seen with light microscope
– One species causes the gonorrhea-like disease
known as chlamydia
• Mycoplasmas – smallest known bacteria
and do not have cell walls
– Can cause one form of pneumonia and one type
of sexually transmitted disease
Cyanobacteria
• Used to be known as blue-green algae, but
are more closely related to bacteria
• They are prokaryotes and have light
trapping pigments for photosynthesis
• Many are blue, but some are black, green or
red (Red Sea)
• Inhabit freshwater and marine environments
(ponds turn green, need algicide in pools)
Protozoa
• Single celled microscopic eukaryotes
• Some cause diseases such as malaria and
sleeping sickness
• Come in many shapes and sizes and some
are capable of photosynthesis
• Classified according to how they move
(flagella, cilia, cytoplasmic extensions
called pseudopodia)
Cilliate
Amoeba
Fungi
• Primary decomposers of organic matter in
the world
• Can cause human diseases such as athlete’s
foot
• Used to be classified as plants but:
– Don’t do photosynthesis – must obtain
preformed food
– Cells have different cell wall
Fungi
• Eukaryotic organisms – 2 groups:
– Yeasts – unicellular, ~ size of large bacteria
• Play a vital role in fermentation of beer and wine
and production of bread
– Molds – long chains of cells seen as fuzzy
masses
Yeast
Mold
Unicellular Algae
• The term algae refers to any plant-like
organisms that practice photosynthesis and
differ structurally from land plants
• Two important algae for microbiology:
– Diatoms
– Dinoflagellates
Diatoms
• Eukaryotic marine organisms
• They are photosynthetic – make carbohydrates
– passed on to other marine organisms when
they are eaten
• Cell walls are impregnated with silicon dioxide
(glasslike)
• When they die their remains accumulate on the
sea floor as diatomaceous earth (used to
produce filters)
Dinoflagellates
• Photosynthetic eukaryotes
• Important in the world’s food chains
• They can also produce periodic red tides in
the oceans
Viruses
• Neither prokaryotes nor eukaryotes
• They are non-cellular, do not grow, do not
show any nutritional pattern
• Only observable activity is replication,
which can only be done inside a living cell
• They are just a fragment of DNA or RNA
inside of a protein sheath
• Cause many human diseases – flu, polio,
hepatitis, chickenpox