Microbiology – Alcamo Lecture: Bacterial Structures -Not all bacteria have all structures

Shapes of Bacteria 3 Different Shapes:

Bacilli Rod shaped Most occur singly, but some form long chains called Streptobacilli Examples: –Typhoid fever –Anthrax –Diptheria

Typhoid Fever Typhoid fever — a common worldwide bacterial disease transmitted by the ingestion of food or water contaminated with the feces of an infected person Caused by the bacterium Salmonella enterica The incubation period is usually 1-2 weeks, and the duration of the illness is about 3-4 weeks. Symptoms include: –Poor appetite –Headaches –Generalized aches and pains –Fever as high as 104 –Lethargy –Diarrhea

Anthrax Anthrax is an acute disease caused by the bacterium Bacillus anthracis. Most forms of the disease are lethal, and it affects both humans and animals. There are effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment. Can form dormant endospores that are able to survive in harsh conditions for decades or even centuries. When spores are inhaled, ingested, or come into contact with a skin lesion on a host, they may become reactivated and multiply rapidly.

Cocci Usually sphere shaped but can be oval Diplococci – cocci that remain in pairs –Examples – Gonorrhea, Menengitis Streptococci – cocci in chains –Examples - Strep throat, Tooth decay Staphylococcus – irregular grape-like cluster of cells –Examples – Food poisoning, staph skin infections

Gonorrhea Also called the "clap" or "drip," gonorrhea is a contagious disease transmitted most often through sexual contact with an infected person. Gonorrhea is caused by Neisseria gonorrhoeae, a bacterium that can grow and multiply easily in mucus membranes of the body. Symptoms: –Greenish yellow or whitish discharge from the penis or vagina –Burning when urinating –Burning in the throat (due to oral sex) –Painful or swollen testicles (in men) –Swollen glands in the throat (due to oral sex)

Meningitis Meningitis is an infection of the membranes (meninges) surrounding the brain and spinal cord. The bacteria most often responsible for bacterial meningitis are common in the environment and can also be found in your nose and respiratory system without causing any harm. Sometimes meningitis occurs for no known reason. Other times it occurs after a head injury or after you have had an infection and your immune system is weakened. The onset of symptoms is fast, within 24 hours. If allowed to progress, you can die from bacterial meningitis.

Spiral Bacteria Vibrios – curved rods - look like a comma –Example - Cholera Spirilla – corkscrew shape with flagella –Example – Rat Bite fever Spirochetes – corkscrew shape but no flagella –Example - syphilis

Cholera Cholera is an infection of the small intestine caused by the bacterium Vibrio cholerae. The main symptoms are watery diarrhea and vomiting. Transmission occurs primarily by drinking water or eating food that has been contaminated by the feces of an infected person, including one with no apparent symptoms.

Syphilis Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidumTreponema pallidum The primary route of transmission is through sexual contact. Primary syphilis - develop one or more sores on the genitals or in or around the mouth Secondary stage - rosy rash typically on the palms of the hands and soles of the feet. Also moist warts in the groin, white patches on the inside of the mouth, swollen lymph glands, fever, and weight loss. Tertiary syphilis - severe problems with the heart, brain, and nerves that result in paralysis, blindness, dementia, deafness, impotence, and death.

Flagella Used by some bacteria to achieve motion Made of long rigid strands of protein called flagellin Protein strands are permanently coiled Permits the flagellum to rotate and propel the bacterium forward

Flagella Complicated structure: Filament attached to hook-like shaft which is inserted through cell wall and attached to cell membrane

Flagella Monotrichous Lophotrichous Amphitrichous Peritrichous

Axial Filament Only spirochete One flagella attached at both ends of flexible spiral MO Motion effected by cell spinning around filament

Pili Look like short flagella but have nothing to do with motion Very tiny protein “Hairs” that enable MO to stick to surfaces - like “Velcro”

Pili Pili aid in transfer of genetic material between bacteria Pili anchor bacteria to surfaces like living tissue Can enhance MO’s disease effect Example - gonorrhea

Capsule Some bacteria secrete a layer of polysaccharides and proteins that stick to its surface Sticky and gelatinous Serves as a buffer between the bacteria and its environment –Protects bacteria against dehydration –Protects bacteria against host’s immune system

Glycocalyx Some bacteria produce a Slime Layer Complex sugar, made inside cell wall secreted as liquid, polymerizes to jelly like substance Cavities – S. mutans attaches itself to teeth by using the sugar a person eats – creates an acid that breaks down tooth enamel

Cell Wall All bacteria have a cell wall except mycoplasmas Semi-rigid structure, protects, gives shape Amount of chemical “Peptidoglycan” determines characteristics of cell wall If a lot: Thick, G+ stain reaction, sensitive to penicillin and lysozyme in tears, saliva, mucous

If small: thinner, G- stain reaction, not sensitive to penicillin or lysozyme If MO is pathogenic, disease more difficult to cure

Cell Membrane Boundary layer of the cell inside of cell wall Contains Cytoplasm, controls molecular traffic in and out of the cell Triple layer structure, 60% proteins, 38% lipids (phospholipid bilayer), 2% sugars Antimicrobials (detergents, alcohol, some antibiotics) dissolve cell membrane

cell membrane animation

Cytoplasm Gelatinous mass of proteins carbohydrates lipids nucleic acids salts ions water

Important Structures in Cytoplasm Ribosomes – protein synthesis Inclusion Bodies – globules of starch or lipids – store nutrients Bacterial Chromosome – closed loop of DNA without a membrane or proteins (nucleoid region) Plasmids – smaller, separate molecules of DNA – few genes but do give bacteria drug resistance (R genes)

Endospores Some Gram + bacteria produce highly resistant structures - spores –Bacteria grow, mature and reproduce as vegetative cells –Then the bacterial chromosome replicates and the cell membrane grows in to seal off a developing spore –Next, thick layers of peptidoglycan form to protect the cell –Finally, the cell wall of the vegetative cell disintegrates and the spore is released

“Sporulation” is spore formation - DNA + some cytoplasm wrapped in spore case formed by cell membrane “Germination” occurs when good environmental conditions return – vegetative cell

Kingdom Classification

Archaeobacteria Have existed on earth longer than any other living organism They are different from eubacteria: –No peptidoglycan in cell wall –Different lipids in cell membrane –Different ribosomal RNA –Now archaeobacteria and eubacteria are classified as different kingdoms

Archaeobacteria 3 Types: –Methanogens – rods that live in anaerobic conditions and produce methane gas – common in marshes and the guts of cows and humans –Thermoacidophiles – resistance to acid and high temperatures – live in hot springs and ocean vents –Extreme Halophiles – thrive in high salt environments (Great Salt Lake)