The cell wall is a structure found in most prokaryotes and some eukaryotes that envelopes the cell membrane. Working in combination with cytoskeletal elements, the cell wall maintains the cell's morphology and protects it from changes in osmotic pressure.

Cell Wall

The cytoplasm consists of organic and inorganic solutes and free floating ribosomes. Chromosomal DNA and plasmids are located in this region.

Cytoplasm

Mesosomes store respiratory enzymes and aid in cellular reproduction. These vesicles are formed by the invagination of the plasma membrane into the cytoplasm. 

Mesosomes

Cytoplasmic inclusions are structures often found in prokaryotic cells that serve to compartmentalize their cytoplasm, despite their general lack of complex membrane-bound organelles. They can store nutrients or gas needed for the cell's metabolism or buoyancy, and they play an important role in reducing the buildup of osmotic pressure as the cell accumulates compounds.

Cytoplasmic Inclusions

Flagella (singular: flagellum) are tail-like cellular structures used for locomotion by some bacteria, archaea, and eukaryotes. Because they are extremely thin, they typically cannot be observed under a standard light microscope without specialized staining techniques.

Flagella

The plasma membrane, also referred to as the cell membrane or cytoplasmic membrane, is a fundamental structure found in all prokaryotic and eukaryotic cells. It encloses the cytoplasm and acts as a semipermeable barrier, exhibiting selective permeability to control the flow of metabolites by allowing specific molecules to enter or leave the cell while restricting the passage of others.

Plasma Membrane

Fimbriae are short, bristle-like protein appendages that project from the bacterial cell surface by the hundreds. Because they are structurally similar to pili, the terms are often used interchangeably, but fimbriae are primarily responsible for enabling a cell to adhere to surfaces and other cells. For pathogenic bacteria, this adherence is critical for colonization, infectivity, and virulence, and it also plays an essential role in biofilm formation.

Fimbriae

The nucleoid is a region within a prokaryotic cell where its DNA and DNA-associated proteins are concentrated. Because prokaryotic cells lack a complex nuclear membrane, their genetic material—which is typically a single, circular, and haploid (unpaired) chromosome—is housed in this specific nucleoid area rather than a true nucleus.

Nucleoid

Ribosomes are made up of RNA and proteins. They are responsible for translating mRNA into proteins. Ribosomes are present in the cytoplasm.

Ribosomes

Endospores are highly resilient, dormant structures formed by certain vegetative bacterial cells when nutrients are depleted or environmental conditions become unfavorable. They protect the bacterial genome and allow the cell to survive for extended periods—up to thousands of years—enduring harsh conditions such as extreme temperatures, radiation, chemicals, and lack of food or water.

Endospores

Some bacteria are capable of forming inclusion bodies which are used for holding excess materials like nutrients or proteins. These cell structures decrease osmotic pressure in the cell by containing these compounds in inclusion bodies. 

Inclusion Bodies

Plasmids are small, circular, double-stranded molecules of extrachromosomal DNA, meaning they are not part of an organism's main chromosome. While most commonly found in bacteria, they can also be present in archaea and eukaryotic organisms. A single cell can contain hundreds of plasmids, which often carry genes that confer advantageous traits, such as antibiotic resistance, that are critical for the organism's survival.

Plasmids

A capsule is a specific type of glycocalyx characterized as an organized layer located immediately outside of the bacterial cell wall. It is typically composed of polysaccharides or proteins. By forming a distinct, clear boundary around the cell, capsules help protect the microbe and facilitate its adherence to surfaces.

Capsule

Many bacterial cells feature protein appendages that are embedded within their cell envelopes and extend outward, enabling them to interact with their external environment. These filamentous appendages, which include fimbriae, pili, and flagella, facilitate crucial functions such as attaching to surfaces, transferring DNA between cells, and providing cellular movement.

Filamentous Protein Appendages

Pili (singular: pilus) are long, relatively sparse protein appendages on the surface of some bacterial cells that primarily facilitate attachment to external surfaces.

Pilus

Prokaryotic cells possess a variety of specialized internal and external structures. A typical rod-shaped bacterium features a thick outer capsule, a thinner cell wall, and an innermost plasma membrane. Externally, it may have long projections called flagella, a shorter projection called a pilus, and numerous very short projections known as fimbriae. Internally, the plasma membrane encloses a fluid called cytoplasm, which contains ribosomes, small spheres called inclusions, a large folded loop of DNA known as the nucleoid, and a small loop of DNA called a plasmid. Other structures sometimes present include mesosomes and endospores.

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Tulane University

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Bacteria are prokaryotic microorganisms found in nearly every habitat on Earth, including within and on the human body. As prokaryotes, their genetic material (DNA) is not housed within a true nucleus. Most bacterial cells feature cell walls containing peptidoglycan. While many bacteria are harmless or beneficial, some act as pathogens and cause diseases in humans and other animals.

Bacteria

Al-mohanna, Moshtaq & H., quine. (2016). MORPHOLOGY AND CLASSIFICATION OF BACTERIA. 

Morphology and Classification of Bacteria

https://openstax.org/details/books/microbiology/

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.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Diseases that require arthropod vectors:
- Anaplasmosis
- Ehrlichiosis
- Epidemic Typhus
- Murine (Endemic) Typhus
- Rocky Mountain Spotted Fever
- Lyme Disease
- Relapsing Fever
- Trench Fever

Zoonotic Febrile Diseases

TSS is caused by a toxemic infection of the pathogen *Staphylococcus aureus*.

Toxic Shock Syndrome (TSS)

Streptococcal Toxic Shock-like Syndrome is caused by the pathogen *Streptococcus pyogenes*. 

Streptococcal Toxic Shock-like Syndrome

Puerperal Sepsis is most often caused by the pathogen *Streptococcus pyogenes*, but can also be caused by *Streptococcus spp., Staphylococcus spp., Enterococcus spp., Chlamydia spp., Escherichia coli, Klebsiella spp., Proteus spp., Peptostreptococcus spp., Bacteroides spp.,* and *Clostridium spp.*

Puerperal Sepsis

Infectious Arthritis can be caused by many bacteria, most notably caused by the pathogens *S. aureus* or *Neisseria gonorrhoeae*. 

Infectious Arthritis

This inflammation of bone tissue is most commonly caused by the pathogen *S. aureus*, but can also be caused by *M. tuberculosis, Pseudomonas aeruginosa, Streptococcus pyogenes, S. agalactiae*, Enterobacteriaceae species, and other microorganisms

Osteomyelitis

Rheumatic Fever is caused by infections of *S. pyogenes* that have nonsuppurative sequelae.

Rheumatic Fever

Bacterial Endocarditis can be caused by an infection of any of the following pathogens: *Staphylococcus aureus, viridans streptococci, Enterococcus faecalis, Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens*, and *Kingella kingae*.

Bacterial Endocarditis 

Bacterial Pericarditis can be caused by *Staphylcoccus spp.* or *Streptococcus spp.*

Bacterial Pericarditis 

Gas Gangrene is caused by the endospores of the pathogen *Clostridium perfringens*.

Gas Gangrene

Tularemia, also known as rabbit fever, is caused by the pathogen *Francisella tularensis*.

Tularemia

There are four pathogens that can cause Brucellosis in humans: *B. abortus, B. canis, B. suis*, and *B. melitensis*.

Brucellosis

Cat Scratch Disease is caused by the pathogen *Bartonella henselae.*

Cat Scratch Disease

Rat-bite fever can be caused by two pathogens: *Streptobacillus moniliformis* or *Spirillum minor*

Rat- Bite Fever

Plagues are a disease that affects humans and other mammals. It is caused by the bacterium, *Yersinia pestis*. Humans usually get the plague after being bitten by a rodent flea that is carrying the plague bacterium or by handling an animal infected with the plague.

Plague

Bacteriology is the study of bacteria and how that affect human health as well as agriculture

Bacteriology

- The Immune System
- CDC
- Morphology and Classification of Bacteria

References for Bacteria

These are diseases caused by bacteria and spread to humans by arthropods.

Vector borne bacterial diseases

Bacteria are classified based on size, shape and arrangement. 

Morphology & Classification of Bacteria

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

Bacterial vaccines are made from whole bacteria, their secreted toxins, or capsular polysaccharides.

- Live-attenuated bacterial vaccine

- Vaccines that generate toxin-specific neutralizing antibodies

- Subunit/Conjugate vaccines

Types of Bacterial Vaccines

Which of the following statements is true about bacteria?

What is a characteristic feature of bacterial cell walls?

Which of the following is true about the nutritional modes of bacteria?

Which of the following bacteria is known to cause tuberculosis?

Bacteria possess diverse metabolic capabilities that allow them to thrive in various environments using different nutrients. Some are photosynthetic, such as oxygenic cyanobacteria and anoxygenic green sulfur and nonsulfur bacteria, which derive energy from sunlight and fix carbon dioxide. In contrast, nonphotosynthetic bacteria obtain their energy from organic or inorganic compounds.

Bacterial Metabolism

Bacterial Structures

Vegetative cells represent the normally active, growing, and metabolizing state of bacterial cells. While bacteria are generally observed as vegetative cells, some genera possess the ability to transition from this state to form dormant endospores when environmental conditions become unfavorable for survival.

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