Do NowClassify the following organisms as

photoautotrophs, chemoautotrophs, photoheterotrophs, or chemoheterotrophs:

1. Basidiomycetes break down dead plant matter for energy and carbon.

2. Cyannobacteria float through water, capturing sunlight and CO2 they need to grow and

reproduce.

3. Acidithiobacilus sulfuroxidans oxidizes hydrogen sulfide for energy, and gets its

carbon from the air.

Classification

• So far, we’ve classified organisms in ways that describe all organisms.

• Today, we’ll learn some bacteria-specific classification schemes.

Test Thursday

• There will be 2 microbiology tests, the first of which will be this Thursday, 10.1

• Topics include items covered by quizzes 1-3, especially classification.

• Also included will be today’s topics as well as other material covered in class.

• Review sheet available tomorrow.

• In class review Wednesday.

Cell Shape, aka Morpology

• Morphology: the form and structure of an organism or any of its parts

• Greek “morphos,” meaning “form” or “shape.”

• Although there are some exceptions, most bacterial cells can be described as cocci, bacilli, or spirochetes.

Cocci = Spheres

Bacilli = Rods

Spirochetes = spirals• Pronounced “sp-eye-row-ketes”

Bacterial Morphology Review

coccus

bacillus

spirochetes

Gram Stain Classification

• This old, dead, white dude developed a procedure now referred to as “Gram staining” in 1884.

• Gram staining classifies bacteria according to differences in their cell walls. There’s only 2 types!

Gram Staining: Under the ‘Scope

Gram positive: purple

Gram negative: pink

Gram + Cell Wall: Lots of Peptidoglycan

“Peptido” = peptides; “glycan” = sugars

• Peptide is a synonym for amino acid.

• Glycan is a type of sugar.

Gram Negative Cell Wall: A Peptidoglycan Sandwich

• The Gram negative cell wall is more complex and has 3 layers:

• Cell membrane, peptidoglycan layer (small), outer membrane.

Why Care?

• Most disease causing bacteria are gram-negative.

• Many antibiotics work by breaking down bacterial cell walls.

• Gram classification helps identify bacteria.

Review

• Classify bacterial cells based on morphology

• Explain the difference between gram positive and gram negative cell walls

• Identify the two types of molecules in peptidoglycan.