Studying the morphology of bacteria requires using microscopes. The types of microscopes are:
- Optical microscope
- Phase contrast microscope
- Dark ground microscope
- Electron microscope

Microscopy

Due to the lack of contrast in light microscopes, observation of structural details in live bacteria is not possible. Staining specimens adds contrast to the image. This involves dying and fixing the specimen, subsequently killing the bacteria. Commonly used staining techniques are:
- Simple Stains
- Negative Staining
- Impregnation Methods
- Differential Stains

Stained Preparations

Individual cells of a specific prokaryotic organism typically exhibit a characteristic shape, known as cell morphology. While thousands of prokaryotic organisms exist, only a handful of morphologies are commonly seen microscopically. These standard shapes include spherical (coccus), rod-shaped (bacillus), curved comma-shaped (vibrio), short oval-like rods (coccobacillus), long rigid corkscrews (spirillum), and loose, flexible helical spirals (spirochete).

Cell Morphologies

Which of the following characteristics are used to classify bacteria?

Which of the following bacterial shapes is correctly matched with its description?

Which of the following arrangements of bacteria is correctly matched with its description?

Which of the following is NOT a common bacterial shape?

In addition to their individual cellular shape, prokaryotic cells of the same species may group together into distinctive arrangements. These characteristic groupings are determined by the plane of cell division. The most commonly observed groupings are the various arrangements of cocci and bacilli.

Common Prokaryotic Cellular Arrangements

Bacteria are classified based on size, shape and arrangement. 

University of Michigan - Ann Arbor

University of Wisconsin - Madison

Tulane University

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

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 a serious disease that occurs when the endospores of *Clostridium perfringens* enter a wound and germinate. The resulting viable bacterial cells produce a toxin that causes the necrosis, or death, of surrounding tissue.

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

Morphology & Classification of Bacteria

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

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.

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.

Vegetative Cells

Shewanella is a genus of deep-sea bacteria adapted to oxygen-scarce environments by growing long appendages equipped with specialized oxygen-seeking sensors. Additionally, Shewanella species can digest toxic waste and generate electricity.

Shewanella

The soil-dwelling bacterium *Paracoccus denitrificans* is capable of surviving extreme gravitational forces. In laboratory studies, it remained viable after being centrifuged at $${}2.4$$ g, which is equivalent to the acceleration on the surface of Jupiter.

Paracoccus denitrificans

Modern bacterial taxonomy classifies bacteria using physiological, biochemical, and genetic traits. This classification includes a unique category of deeply branching bacteria, which represent the oldest evolutionary lineages. Additionally, gram-negative bacteria are further divided into Proteobacteria, Cytophaga-Flavobacterium-Bacteroides (CFB), and spirochetes, while gram-positive and other bacterial groups continue to be categorized based on their distinct physiological and genomic properties.

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