Prokaryotic Cells BACTERIA. The Prokaryotic Cell Members of the prokaryotic world make up a vast...
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Prokaryotic Cells BACTERIA. The Prokaryotic Cell Members of the prokaryotic world make up a vast heterogeneous group of very small single-celled organisms
The Prokaryotic Cell Members of the prokaryotic world make up a
vast heterogeneous group of very small single-celled organisms.
Include bacteria and archae, although the majority are bacteria The
thousands species of bacteria are differentiated by many factors
such as: Morphology (shape), chemical composition (often detected
by staining reactions), nutritional requirements, biochemical
activities, and sources of energy (sunlight or chemicals) These
differences can only be seen with the use of a microscope
Slide 3
Size, Shape, and Arrangement Bacteria come in many sizes, and
several shapes. Most range from 0.2 to 2.0 m in diameter and 2-8 m
in length Basic shapes include: Cocci- round shaped Bacillus - rod
shaped Spirillum- spiral shaped, helical shape like corkscrew, have
rigid bodies, and use flagella to move Vibrio - curved Spirochetes-
helical and flexible, move by axial filaments found within flexible
external sheath Square Star
Slide 4
Cell Cluster Formation Bacteria are also classified according
to cell cluster formation: Streptobacillus Cluster
formationDescription Diplococci Two cocci cells paired
StaphylococciNumber of cells clustered together ( grape-like )
Streptococci & Streptobacillus Number of cells arranged in a
chain
Slide 5
vibriobacillus spirochete coccusspirillumbacillus Learning
Check: What Shape are these bacteria? 1.1. 2.2. 3.3. 5.5. 6.6.
Slide 6
Shape and Arrangement The shape of bacteria is determined by
heredity. Most bacteria are monomorphic : maintain a single shape
Environmental factors can alter that shape Some bacteria like
Rhizobium and Corynebacterium are pleomorphic : can have many
shapes, not just one. Source for figure:
http://textbookofbacteriology.net/Impact_2.html
Slide 7
*Cell wall- Most bacteria have a cell wall but there are some
that do not like Mycoplasma species Basic Components of
Bacteria
Slide 8
Structures External to the Cell Wall Possible structures
external to the prokaryotic cell wall are: Glycolax Flagella Axial
filaments Fimbrae and Pili
Slide 9
What is the Glycocalyx? Means sugar coat & is the general
term used for substances that surround cells Bacterial glycocalyx
is a viscous (sticky), gelatinous polymer that is external to the
cell wall Composed of a polysaccharide, polypeptide, or both Two
types: Capsule: substance is organized and is firmly attached to
the cell wall Slime layer: substance is unorganized and only
loosely attached to the cell wall glycocalyx Fig. 1 Source for Fig.
1:
http://emp.byui.edu/wellerg/The%20Cell%20Lab/Prokaryotic%20Cells/The%20Prokaryotic%20Cell.html
Slide 10
(a) Micrograph of Streptococcus pneumoniae, the common cause of
pneumonia, showing a prominent capsule. (b) Bacteroides, a common
fecal bacterium, has a slime layer surrounding the cell
Slide 11
Slide 12
Learning Check What advantage does a glycocalyx provide a cell?
(think about its composition)
Slide 13
Glycocalyx Very important component of biofilms Biofilms are
densely packed communities of microbial cells that grow on living
or inert surfaces A glycocalyx that helps cells in a biofilm attach
to their target environment and to each other is called an
extracellular polymeric substance (EPS) EPS protects the cells
within it Facilitates communication among them and enables the
cells to survive by attaching to various surfaces in their natural
environment Source for Fig. 2
http://www.microbiologybytes.com/blog/2010/09/08/the-biofilm-matrix/
Fig. 2
Slide 14
Flagella Some prokaryotes have flagella which are long
filamentous appendages that propel bacteria Peritrichous : flagella
distributed over the entire cell Polar: at one or both poles or
ends of the cell Monotrichous: A single flagellum at one pole
Lopothrichous: a tuft of flagella coming from one pole
Amphitrichous: flagella at both poles of the cell Bacteria that
lack flagella re referred to as atrichous (without
projections)
Slide 15
Flagellar Movement Figure 3.9 Motion of a peritrichous
bacterium. In peritrichous bacteria, runs occur when all of the
agella rotate counterclockwise and become bundled. Tumbles occur
when the agella rotate clockwise, become unbundled, and the cell
spins randomly. In positive chemotaxis (shown), runs last longer
than tumbles, resulting in motion toward the chemical
attractant.
Slide 16
Axial Filaments Spirochetes have unique structure and motility
Move my means of axial filaments Bundles of fibrils that arise at
the ends of the cell beneath an outer sheath and spiral around the
cell The rotation of the filaments produces a movement of the outer
sheath that propels the spirochetes in a spiral motion
Slide 17
Fimbriae and Pili Many gram-negative bacteria contain hair-like
appendages that are shorter, straighter, and thinner than flagella
are used for attachment and transfer of DNA rather than for
motility Fimbrae can occur at the poles of the bacterial cell or
entire surface of cell H ave a tendency to adhere to each other and
to surfaces Pili are usually longer than fimbrae but shorter than
flagella and are found as one or two per cell Involved in motility
and DNA transfer
Slide 18
Conjugation Pili
Slide 19
Learning Check Several Escherichia coli cells are connected by
conjugation pili. How are pili different from bacterial
agella?