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PROKARYOTICYUSRON SUGIARTO
All cells discovered thus far are classified into one of two fundamentally different groups:
1. the small, seemingly simple prokaryotic cells2. the larger, structurally more complicated
eukaryotic cells
MICROBIOLOGYPROCARIOTIC
BASIC CHARACTERISTICS OF CELLS AND LIFE FORMS
MICROBIOLOGYPROCARIOTIC
BASIC CHARACTERISTICS OF CELLS AND LIFE FORMS
are found in animals, plants, fungi, and protists.
They contain a number of complex internal parts called organelles that perform useful functions for the cell.
By convention, organelles are defined as cell components enclosed by membranes that carry out specific activities involving metabolism, nutrition, and synthesis.
Organelles also partition the eukaryotic cell into smaller compartments.
EUKARYOTIC CELLS
are found only in the bacteria and archaea.
Sometimes it may seem that prokaryotes are the microbial “havenots” because, for the sake of comparison, they are described by what they lack.
They have no nucleus or other organelles.
PROKARYOTIC CELLS
Prokaryote Genetics
NUCLEOID
• Region of cytoplasm where prokaryotes genomeis located.
• Usually a singular, circular chromosome.
PLASMID• Small extra piece of chromosome/genetic
material.
• 5 - 100 genes
• Not critical to everyday functions.
• Can provide genetic information for
- Antibiotic resistance
- Virulence factors: Molecules produced by pathogen that help it cause disease & thrive.
- Promoting conjugation: Transfer of genetic material between bacteria through cell-to-cell contact.
Image: Prokaryotic Cell Diagram: M. Ruiz, Bacterial conjugation, AdenosineFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
CELL SHAPES
Coccus / Arrangement
Bacillus / Arrangement
Other Shapes
MICROBIOLOGYPROCARIOTIC
CELL SHAPES
(a)Staphylococcus aureus
(b)Enterococcus faecalis
(c)Bacillus megaterium
(d)Rhodospirillum rubrum
(e)Vibrio cholerae
MICROBIOLOGYPROCARIOTIC
CELL SHAPES
MICROBIOLOGYPROCARIOTIC
FUNCTIONS OF PROCARYOTIC STRUCTURES
MICROBIOLOGYPROCARIOTIC
FUNCTIONS OF PROCARYOTIC STRUCTURES
MICROBIOLOGYPROCARIOTIC
PLASMA MEMBRANE
Most membrane-associated lipids are structurally asymmetric with polar and nonpolar ends and are called amphipathic.
The polar ends interact with water and are hydrophilic; the nonpolar hydrophobic ends are insoluble in water and tend to associate with one another.
This property of lipids enables them to form a bilayer in membranes. The outer surfaces are hydrophilic, whereas hydrophobic ends are buried in the interior away from the surrounding water.
• Separates the cell from its environment.
• Phospholipid molecules oriented so that HIDROPHILIC water-loving heads directed outward and HYDROPHOBIC water-hating tails directed inward.
• Proteins embedded in two layers of phospholipids (lipid bilayer).
• Membrane is semi-permeable. Q:What does that mean?
Image: Cell Membrane diagram, Dhatfield From the Virtual Cell Biology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
PLASMA MEMBRANE
MICROBIOLOGYPROCARIOTIC
This diagram of the fluid mosaic model of bacterial membrane structure shows the integral proteins (blue) floating in a lipid bilayer. Peripheral proteins (purple) are associatedloosely with the inner membrane surface. Small spheres represent the hydrophilic ends of membrane phospholipids and wiggly tails, the hydrophobic fatty acid chains. Other membrane lipids such as hopanoids (pink) may be present. For the sake of clarity, phospholipids are shown in proportionately much larger size than in real membranes.
PLASMA MEMBRANE STRUCTURE
Prokaryotes – Plasma Membrane as a Barrier
OSMOSIS• Is the diffusion of water across a semi-
permeable membrane.
• Environment surrounding cells may contain amounts of dissolved substances (solutes) that are…
- equal to
- less than
- greater than
…those found within the cell.
Images: Osmosis animation; Osmosis with RBCs, M. Ruiz
CELL
Plasma
membrane
Liquid
environment
outside the cell.
Liquid
environment
inside the cell.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Prokaryotes – Plasma Membrane as a Barrier
Tonicity and Osmosis
ISOTONIC: equal concentration of a solute inside and outside of cell.
HYPERTONIC: a higher concentration of solute.
HYPOTONIC: a lower concentration of solute.
Images: Osmosis animation; Osmosis with RBCs, M. Ruiz
Water will always move toward a hypertonic
environment!!
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
ACTIVE TRANSPORT
• How most molecules move across the plasma membrane.
• Analogous to a pump moving water uphill.
• Types of active transport are classified by type of energy used to drive molecules across membranes.
Image: Sodium-potassium pump, M. Ruiz
ATP Driven Active Transport
Energy from adenosine triphosphate (ATP) drives substances across the plasma membrane with the aid of carrier molecules.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
INTERNAL MEMBRANE SYSTEMS
Mesosome Structure.Bacillus fastidiosus. A large mesosome lies adjacent to the nucleoid
membranous structures of several kinds can be observed, A commonly observed structure is the mesosome.
Mesosomes are invaginations of the plasma membrane in the shape of vesicles, tubules, or lamellae
they may be involved in cell wall formation during division or play a role in chromosome replication and distribution to daughter cells
MICROBIOLOGYPROCARIOTIC
INTERNAL MEMBRANE SYSTEMS
THE GRAM-POSITIVE ENVELOPE THE GRAM-NEGATIVE ENVELOPE
Peptidoglycan is a huge polymer of interlocking chains of identical peptidoglycan monomers.
Provides rigid support while freely permeable to solutes.
Backbone of peptidoglycan molecule composed of two derivatives of glucose:
- N-acetylglucosamine (NAG)- N-acetlymuramic acid (NAM)
NAG / NAM strands are connected by inter-peptide bridges.
Prokaryotes – Cell Wall
Image: Bonding structure peptidoglycan, Mouagip; Other Image Source UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
INTERNAL MEMBRANE SYSTEMS
The gram-positive envelope is from Bacillus licheniformis(left), and the gram-negative micrograph is of Aquaspirillum serpens(right).
M; peptidoglycan or murein layer; OM, outer membrane; PM, plasma membrane; P, periplasmic space; W, gram-positive peptidoglycan wall
From the peptidoglycan inwards all bacteria are very similar. Going further out, the bacterial world divides into two major classes (plus a couple of odd types). These are:
Gram ___________ Gram ___________
Prokaryotes - Cell Wall
Images: Staph, Gram Stain, SPO Microbiology Images, T. Port; E coli, Y tambeFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
Prokaryotes - Cell WallGram-Positive & Gram-Negative
Images: Sources UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
Prokaryotes - Cell WallGram-Positive & Gram-Negative
Image: Gram-positive cell wall schematic, Wiki; Gram-negative cell wall schematic, Jeff DahlFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
Q: Why are these differences in cell wall structure so important?
Images: Prokaryotic Cell: M. Ruiz, Other Images, Sources UnknownFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
THE BACTERIAL ENDOSPORE
A number of gram-positive bacteria can form a special resistant, dormant structure called an endospore.
These structures are extraordinarily resistant to environmental stresses such as heat, ultraviolet radiation, gamma radiation, chemical disinfectants, and desiccation.
PROKARYOTES - ENDOSPORES
Dormant, tough, non-reproductive structure produced by small number of bacteria.
Q: What is the function of endospores?
Resistant to radiation, desiccation, lysozyme, temperature, starvation, and chemical disinfectants.
Endospores are commonly found in soil and water, where they may survive for very long periods of time.
Image: Bacillus subtilis, SPO Science Image Library, Endospore stain from Dr. Ronald E. Hurlbert, Microbiology 101 lab manualFrom the Virtual Microbiology Classroom on ScienceProfOnline.com
An endospore stained bacterial smear of Bacillus subtilis showing endospores as green and
vegetative cells as red.
Meet the Microbe: _______________(Gram+)
The members of this genus have a couple of bacterial “superpowers” that make them particularly tough pathogens.
Q: Anyone know what those superpowers are?
Clostridia are known to produce a variety of toxins, some of which are fatal.
- Clostridium tetani = agent of tetanus
- C. botulinum = agent of botulism
- C. perfringens = one of the agents of gas gangrene
- C. difficile = part of natural intestinal flora, but resistant strains can proliferate and cause pseudomembranous colitis.
Images: Man with Tetanus, Sir Charles Bell; Clostridium botulinum, PHIL #2107; Wet Gangrene, Wiki From the Virtual Microbiology Classroom on ScienceProfOnline.com
MICROBIOLOGYPROCARIOTIC
THE BACTERIAL ENDOSPOREENDOSPORE FORMATION: LIFE CYCLE OF BACILLUS MEGATERIUM
Confused?Here are links to fun resources that further explain aerobic
respiration:
• Cell Structure: Prokaryotes Main Page on the Virtual Micrboiology Classroom of Science Prof Online.
• Prokaryotic Cell: Structures, Functions & Diagrams, an article from
SPO.
• Prokaryotic & Eukaryotic: Two Types of Biological Cells, an article from SPO.
• “Got the Time” music video by Anthrax.
• Prokaryotic Cell interactive diagram from Cells Alive website.
• “How big is a…” interactive diagram from Cells Alive website.
• Cell Structure tutorials and quizzes from Interactive Concepts in Biochemistry.
• How Osmosis Works, animation from McGraw-Hill.
• “Germs”. Music by Weird Al Yankovic. Video by RevLucio.
• Bacterial Pathogen Pronunciation Station, a webpage with links to audio files containing the pronunciation of the bacterial names, created by Neal R. Chamberlain, Ph.D.
• Biology4Kids – Cell Biology Main Page by Raders.
(You must be in PPT slideshow view to click on links.)
From the Virtual Microbiology Classroom on ScienceProfOnline.com
Homework Assignment
At the end of some lectures, I will give you homework to evaluate your understanding of that day’s material.
This homework will always be open-book.
Today you may be given an activity on the topic of Osmosis.
If assigned, this assignment will be due at the at the start of class, next time we meet for lecture.
From the Virtual Microbiology Classroom on ScienceProfOnline.com
See the ScienceProfOnline Virtual Microbiology Classroom Diffusion,
Osmosis & Active Transport lecture for a printable Word .doc of this assignment.
Images: Osmosis animation
• practice test questions
• review questions
• study guides and learning objectives
You can access the VMC by going to the Science Prof Online website www.ScienceProfOnline.com
Images: Clostridium difficile, Giant Microbes; Prokaryotic cell, Mariana Ruiz
Are microbes intimidating you?
Do yourself a favor. Use the…
Virtual Microbiology Classroom (VMC) !
The VMC is full of resources to help you succeed, including:
