Bacteria
Unique yet Ubiquitous
Bacteria, a Recap
• Prokaryotic cells that make up the
kingdom of Eubacteria
– Single celled organisms that lack membrane
bound organelles such as a nucleus,
mitochondria, Golgi apparatus etc.
• Reproduce asexually
• Variety of ‘lifestyles’
– Autotroph, heterotroph, aerobic, anaerobic
• Could be harmful or helpful
Shapin’ Up to do Some Work
Bacterial Structure and Function
• Bacteria are the smallest life forms on the planet
so how do we know what they look like and why do we care?
– With the aid of powerful microscopes scientists are able to see bacterial
cell and even dissect them to test their chemical composition
• Bacteria are classified based on three characteristics
– Cell shape
– Cell wall structure
– Motilitiy
• All bacteria have the same general components
–
–
–
–
Cell wall
Cell Membrane
Free floating DNA
ribosomes
Bacterial Cell Shape
• There are three basic cell shapes
– Cocci, spherical cells
• Growing in clusters called staphlococcus
– Staphlococcus aureus
• Growing in chains called sreptococcus
– Streptococcus pneumoniae
– Bacillus, rod shaped cells
• Bacillus anthracis
– Spirillum, curved or spiral shaped cells
• Borrelia burgdorferi
Cell Wall Structure
• All bacterial cells have cell walls, but not all walls are
created equally
• Acts are protection and maintains cell shape
• Cell wall type 1
– Composed of peptidoglycan, a protein sugar combination, thick and strong
– Gram positive
• Cell wall type 2
– Composed of less peptidoglycan but has an additional membrane surrounding it
– Gram negative
Gram staining is a technique used to
separate bacteria based on their cell wall
structure.
Proccess uses two different stains with
washing in between.
If the bacterium holds the gram stain it is
said to be gram positive. If it loses the
stain it is said to be gram negative.
I Like to Move It Move IT!!
• Only half of all prokaryotes have motility
• Being able to move allows a bacterium to…
– Travel towards food
– Move to or away from light or chemical stimuli
– Move toward or away from oxygen
• The most common motility structure is the flagellum
– Long whip like structure protruding out of one oend of the
bacterium
• Other organisms secrete a mucous that they slide
through
• Spirillum bacteria move via whip like action
How’d they get the POWER
• Bacteria have four distinct ways of getting
energy
• Please see Table 2.1 in your text book on
pg 33, copy it out in this space.
The Masters of Asexual Reproduction
•
Binary fission
– Main mode of bacterial reproduction
– Quick and easy
• Exact copy is made of a bacterial cell, DNA, cell membrane and cell wall are all
duplicated, once complete the new bacterial cell pinches itself off of the parent
bacterium
• Copying can take as little as 20 min. = 68 billion cells in 12hrs!!!
• No genetic variability, no bacterial evolution
•
•
Transformation and Conjugation allow for genetic material to mix and
recombine
Transformation
– Bacteria pick up small fragments of DNA from their environment
– Incorporate it into their own DNA and make copies
•
Conjugation
– Two bacterial cells fuse, share DNA in the form of plasmids then separate
– The plasmid copies itself in the original cell before it transfers into the conjugate
cell
•
Transduction
– New genetic material is introduced via viruses
Binary Fission and Conjugation
Tricks of the Trade, the Key to Bacterial
Survival
• Bacteria are among the oldest forms of life, how
and why have they been so successful?
–
–
–
–
Rapid reproduction
Modes of evolution
Diverse lifestyles
Ability to exist as an endospore
• Endospore is a dormant bacterial cell
• Under extreme conditions that do not allow reproduction a
bacterial cell protects the esstials with a thick coat, becoming
very small and dry
• Upon favorable conditins the endospore absorbs moisture,
grows to full size and begins its life cycle
Bacterial Endospore