Discovering the Bacterial Cell

Advanced Biotechnology(c)(5)(b)

The Importance of Bacteria Bacteria are extremely important in the

biosphere Food Production

Examples? Nutrient Cycling

Such as nitrogen fixation in soil Genetic engineering

Bacterial cells transformed Agrobacterium-mediated recombination

"Nitrogen Cycle.“ http://commons.wikimedia.org/wiki/File:Nitrogen_Cycle.svg

Nitrogen Fixation Cycle

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_species.jpghttp://en.wikipedia.org/wiki/Bacillus#mediaviewer/File:Bacillus_subtilis_Gram.jpg

Spiral

http://commons.wikimedia.org/wiki/File:ARS_Campylobacter_jejuni.jpg

https://www.ebiomedia.com/images/stories/BioGalleries/NoteBook/cantlivewithoutum/spirals.jpg

http://sciweb.hfcc.net/biology/jacobs/bio131/cells/images/spiro100b

Filamentous

http://www.environmentalleverage.com/filaments/slides/p_0035.jpghttp://3.bp.blogspot.com/-q9p215SPAgg/T8J2T0v1ZeI/AAAAAAAAAGA/5Jxjf_pj0hQ/s1600/40X_SoilIsolate_1.JPG

http://ulsfmovie.org/images/filamentous-bacteria-microthrix-parvicella.jpg

Bacterial Cell Structures

Pili and fimbriae are interchangeable

Pili: hair-like appendage found on the

surface of many bacterial.

Used for attachment to surfaces, and

gene transfer

Pili / Fimbriae

http://www.daviddarling.info/images/pili.jpg

Flagellum: leash-like appendage

protruding from the body.

Primary role is movement.

Also used as a sensory organelle.

Flagellum

http://www.pleaseconvinceme.com/wp-content/uploads/2012/09/bacteria1.jpg

The ribosome is a complex molecular machine

serving as the primary site of protein biosynthesis.

Ribosomes

Functional protein

Export polypeptide to cytoplasm

Link together amino acids collected from cytoplasm by

tRNA

Translate mRNA

Ribosomes

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

Plasmid

Cytoplasm comprises the gel-like

substance within the cell membrane and

all organelles. All contents of the cell are

contained in the cytoplasm.

Cytoplasm

http://www.learner.org/courses/essential/life/images/show1.cytoplasm.jpg

The cell envelope contains the:

Capsule

Cell Wall

Plasma membrane

Cell Envelope

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

Capsule

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.

Cell Wall

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.

Plasma Membrane

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)

Nucleoid

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

Describe the following structures and their importance:

Pili / Frimbraie

Flagellum

Ribosomes

Plasmid

Cytoplasm

Cell envelope:

Cell wall Peptidoglycan

Plasma membrane

Capsule

Nucleoid

Summary: Organelles

Developed for the Texas Education AgencyEducational Excellence for AFNR project

under contract with theDepartment of Agricultural Leadership,

Education & Communications,Texas A&M University

© Texas Education Agency, 2014Authors: Ian Sprouse, Kirk C. Edney PhD