In gram positive bacteria, the NAM molecules of peptidoglycan are linked with tetrapaptide links. These tetrapeptide molecules are not present in gram negative bacteria. In gram positive bacteria, the peptidoglycan later is much larger compared to gram negative bacteria. They also have a layer of teichoic acid on the external side of the plasma membrane which makes the wall more rigid.

Gram Positive Cell Walls

The class *Actinobacteria* is also called the high G+C gram positive bacteria because their genomes have over 50% guanine and cytosine base pairs. While their class is very diverse in size and biomes they inhabit, one of their important features is that they have distinct and different peptidoglycans in their cell walls.

 High G+C gram positive bacteria: *Actinobacteria*

Low G+C gram positive bacteria have less than 50% cytosines and guanines their genomes. This group of bacteria also contains many pathogens. They consist of many different bacteria: 
- Clostridia
- Lactobacillales
- Bacilli
- Mycoplasmas 

Low G+C gram positive bacteria

Gram positive bacteria have a specific cell wall with a thick peptidoglycan layer. They have been identified from the Gram stain because of their cell wall retains the Gram stain. They have also been further classified by their genomes: 
- High G+C gram positive bacteria
- Low G+C gram positive bacteria

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Bacteria are diverse in their functions, structure and genomes. Some important classes and phyla among bacteria are:
- Proteobacteria
- Nonproteobacteria Gram-Negative Bacteria 
- Phototrophic Bacteria
- Gram-Positive Bacteria
- Deeply Branching Bacteria

Bacterial Diversity

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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This is a phylum of bacteria coiled from microbiologist Carl Woese. These were classified based on their similar genomes. 

Proteobacteria

Phototrophic bacteria use sunlight as their energy source. Phototrophic bacteria consist of many groups: 
- Purple and Green bacteria
- Cyanobacteria

Phototrophic Bacteria

Deeply branching bacteria are the bacteria that represent the oldest living species on Earth that are known. Their name refers to their position on the bottom of the phylogenetic tree where they branch close to the last universal common ancestor. 

Deeply Branching Bacteria

Gram Positive Bacteria

The gram negative bacteria that are not present in the Proteobacteria phylum consist of some of these classes and genera of bacteria:
-  *Chlamidia*
- Spirochetes
- *Cytophaga, Fusobacterium, and Bacteroides*
- Planctomycetes

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