Discovering the Bacterial Cell
Advanced Biotechnology
(c)(5)(b)
The Importance of Bacteria

Bacteria are extremely important in the biosphere

Food Production


Nutrient Cycling


Examples?
Such as nitrogen fixation in soil
Genetic engineering

Bacterial cells transformed

Agrobacterium-mediated recombination
Nitrogen Fixation Cycle
"Nitrogen Cycle.“ http://commons.wikimedia.org/wiki/File:Nitrogen_Cycle.svg
Bacterial Cells
 Bacterial
is a large domain of prokaryotic
microorganisms
 Prokaryote: single-celled organisms lacking a
membrane bound nucleus

Microorganism: microscopic living organisms, either
single celled or multicellular

Even though bacteria are relatively simple, they boast a
well-developed cellular structure responsible for their many
unique functions

Organelle: subunit within a cell with a specific function.
Cell Morphology
 Bacterial
cells have different shapes.
Some examples:
 Coccus
– spheres
 Bacillus
– round-ended cylinders
 Spiral
– twisting
 Filamentous
– very long thin rods,
many times longer than wide
Coccus
http://aqkhanacadmey.webs.com/photos/BIOLOGY-PRACTICAL/cocci%20bactaria.jpg
http://biology.clc.uc.edu/fankhauser/Labs/Microbiology/Buccal&Tooth/sarcinae_P7060987.jpg
Bacillus
http://en.wikipedia.org/wiki/Bacillus#mediaviewer/File:Bacillus_subtilis_Gram.jpg
http://en.wikipedia.org/wiki/Bacillus#mediaviewer/File:Bacillus_species.jpg
Spiral
https://www.ebiomedia.com/images/stories/BioGalleries/Note
Book/cantlivewithoutum/spirals.jpg
http://commons.wikimedia.org/wiki/File:ARS_Campylobacter
_jejuni.jpg
http://sciweb.hfcc.net/biology/jacobs/bio131/cells/images/spiro100b
Filamentous
http://3.bp.blogspot.com/q9p215SPAgg/T8J2T0v1ZeI/AAAAAAAAAGA/5Jxjf_pj0hQ/s1600/40X_S
oilIsolate_1.JPG
http://www.environmentalleverage.com/filaments/slides/p_0035.jpg
http://ulsfmovie.org/images/filamentous-bacteria-microthrix-parvicella.jpg
Bacterial Cell Structures
Pili / Fimbriae
 Pili
and fimbriae are interchangeable
 Pili:
hair-like appendage found on the
surface of many bacterial.
 Used
for attachment to surfaces, and
gene transfer
http://www.daviddarling.info/images/pili.jpg
Flagellum
 Flagellum:
leash-like appendage
protruding from the body.
 Primary
 Also
role is movement.
used as a sensory organelle.
http://www.pleaseconvinceme.com/wpcontent/uploads/2012/09/bacteria1.jpg
Ribosomes
The ribosome is a complex molecular machine
serving as the primary site of protein biosynthesis.
Translate mRNA
Link together amino acids collected
from cytoplasm by tRNA
Export polypeptide to
cytoplasm
Functional protein
Ribosomes
Plasmid
 Plasmids
are small DNA molecules within a
cell that is separate from chromosomal
DNA. This makes it extrachromosomal DNA.

Plasmids carry genes benefitting survival of
the cell. They carry extra information

Artificial plasmids are used as vectors in
molecular cloning.

Drives the replication of recombinant DNA
sequences in host organisms
Plasmid
Cytoplasm
 Cytoplasm
comprises the gel-like
substance within the cell membrane and
all organelles. All contents of the cell are
contained in the cytoplasm.
http://www.learner.org/courses/essential/life/images/show1.cytoplasm.jpg
Cell Envelope
 The
cell envelope contains the:

Capsule

Cell Wall

Plasma membrane
Capsule
 The
capsule is the outer envelope of the
bacterial cell. The capsule is well-organized
and not easily washed off. Help prevent water
loss

The capsule can be the cause of diseases,
but also can play a role in the development of
vaccines
Cell Wall
 The
cell wall of bacterial cells is a distinctive
structure compared to plant and animal cells.


Cell wall made of peptidoglycan.
The cell wall has two types:
 gram-positive

and gram-negative.
Determined through reaction of
cell walls to Gram stain.
 Peptidoglycan
levels play an important role in this.
Plasma Membrane

The plasma membrane is composed of a
phospholipid bilayer. Acts as a permeability
barrier, and location for the transport of
molecules into the cell.

The phospholipid bilayer is a layer of two lipid
layers that form a barrier around cells. It is
found in almost all living organisms.
Nucleoid

The nucleoid contains all/most of the genetic
material. It is NOT a nucleus because it is not
surrounded by a nuclear membrane.

Approx. 60% DNA with small amounts of RNA
and protein (later is generally mRNA and
transcription factors)
Summary

Why are bacterial cells important?

They perform activities essential for our every day
survival: nutrient cycling, food production, microbial
flora in our gut, etc.
 What
is a Prokaryote?
 single-celled
organisms lacking a membrane bound
nucleus
 What

is an organelle?
subunit within a cell with a specific function.
Summary: Organelles
 Describe the following structures and their importance:

Pili / Frimbraie

Flagellum

Ribosomes

Plasmid

Cytoplasm

Cell envelope:

Cell wall


Peptidoglycan

Plasma membrane

Capsule
Nucleoid
Developed for the Texas Education Agency
Educational Excellence for AFNR project
under contract with the
Department of Agricultural Leadership, Education
& Communications,
Texas A&M University
© Texas Education Agency, 2014
Authors: Ian Sprouse, Kirk C. Edney PhD