Prokaryotes Classifying Prokaryotes Identifying Prokaryotes Role in the Environment Bacteria and Disease

Classifying Prokaryotes Eubacteria Larger and more diverse than archaebacteria Live almost everywhere Cell walls contain peptidoglycan Archaebacteria Live in hostile environments (hot springs, salt lakes) Cell walls lack peptidoglycan

Archaea are classified into three main groups: Prokaryote Diversity Below: halophiles living in evaporating salt flats. The colors are caused by pigments in their cells. Halophiles – “salt – loving” Thermophiles – “heat – loving” Methanogens – methane users or makers Thought Question: Prokaryotes such as these halophiles, have unusual metabolisms and occupy niches that eukaryotes could not survive in. How does the concept of adaptive radiation help explain why prokaryotes live in more diverse habitats than eukaryotes? Left: Thermophiles living in a hot spring.

The Three Domains of Life - a cladogram based on ribosomal RNA comparisons. According to this cladogram, which group of bacteria are more closely related to us?

Bacteria often have one of three shapes: Thought Question: What shape are the bacteria on the tip of this needle? bacilli (rod-shaped) spirilli (spiral-shaped) cocci (sphere-shaped)

Unique structures in bacteria: Anatomy of a Bacterium Unique structures in bacteria: Peptidoglycan Cell wall Cell membrane Ribosome Flagellum DNA Pili Peptidoglycan – a carbohydrate/protein layer that forms the cell wall (not in archaea) Peptidoglycan Flagellum – used for locomotion Plasmid Plasmid Pili – used for attachment Plasmid – small, circular sequences of DNA, used in “swapping genes” Flagellum Pili

Gram Staining - a technique used to distinguish between types of eubacteria by measuring the amount of peptidoglycan in the cell wall Gram positive - bacteria with a thick peptidoglycan cell wall, absorbs a purple colored stain = “gram positive bacteria” Gram negative - bacteria with a thin peptidoglycan cell wall, masked by an outer membrane, absorbs red colored stain = “gram negative bacteria”

Obtaining Energy Autotrophs Photosynthesis Cyanobacteria – contain a bluish-green pigment and chlorophyll, common in aquatic environments Chemosynthesis Obtain energy directly from inorganic molecules, found around ocean vents Heterotrophs Can be consumers, parasites, or decomposers Photoheterotrophs Can capture sunlight for energy Also need organic compounds for nutrition

Growth and Reproduction Binary fission DNA replicates and cell divides to produce two identical daughter cells Conjugation Two cells are joined by a bridge and exchange genes (plasmids) – increases diversity Spore Formation Occurs when conditions are unfavorable Can survive months to centuries!

Prokaryotes and the “Invention of Sex” Unlike many eukaryotes, prokaryotes reproduce asexually. Through binary fission (the replication of DNA and the division of one bacterium into two cells) bacteria can typically reproduce much faster than eukaryotes. A disadvantage with this system is that bacteria do not “mix” genes to produce variable offspring. To get around this process bacteria evolved conjugation – the copying & “swapping” of genes between cells, especially when the environment is unfavorable. The mixing of genes between two different individuals is, biologically, sex. Thought Question: How does conjugation enable bacteria to evolve & adapt to new environmental conditions?

Prokaryotes and the Nitrogen Cycle N2 in Atmosphere Nitrogen fixing bacteria - convert nitrogen gas (N2) in the air to an organic form (ammonia, NH3) , usable by some other living things. Nitrifying bacteria - convert ammonia to nitrate (NO3), which is usable for plants to make protein. Decomposing bacteria - break complex organic nitrogen in dead organisms back into NH3). Denitrifying bacteria - break organic simple nitrogen in dead organisms back into N2 gas. NO3- and NO2- NH3

Bacteria infect living organisms by: Bacteria infect living organisms by: * Eating the organism’s tissues directly * Releasing toxins Common Diseases Caused by Bacteria Disease Pathogen Prevention Tooth decay Lyme disease Tetanus Tuberculosis Salmonella food poisoning Pneumonia Cholera Streptococcus mutans Borrelia burgdorferi Clostridium tetani Mycobacterium tuberculosis Salmonella enteritidis Streptococcus pneumoniae Vibrio cholerae Regular dental hygiene Protection from tick bites Current tetanus vaccination Vaccination Proper food-handling practices Maintaining good health Clean water supplies

Characteristics of a Virus Viral Infection Viruses and Disease

Characteristics of Viruses: • Viruses are nonliving, infectious particles (cannot reproduce on their own, cannot obtain energy or feed in any way) • Viruses are extremely small (on average they are one-thousandth the size of a typical bacterium) • Vary greatly in structure and shape • All organisms can be infected by viruses

Virus Structures - all viruses contain a protein capsid (coat), nucleic acid (RNA or DNA), and some means of attaching to and entering a host cell. Tobacco Mosaic Virus T4 Bacteriophage Influenza Virus RNA Capsid proteins Head Tail sheath DNA Tail fiber RNA Capsid Surface proteins Membrane envelope Thought Question: Unlike bacteria, viruses cannot be treated with antibiotics since they lack a peptidoglycan cell wall. Instead, we can only prevent viruses with vaccines – drugs made by destroyed viruses. What part of the virus do you think is most important to making a vaccine so the body can “recognize” and destroy the virus?

Virus Reproduction: The proteins of the capsid allow the virus to gain entry through the cell membrane of the host Viruses infect a host by injecting their DNA or RNA. Infected cells make copies of the virus’ genetic material instead of its own The parasitic virus “hijacks” the cellular machinery of the cell. Thought Question: What organelle do viruses lack that are required for reproduction? Explain.

Reproductive Cycles of a Virus Lytic cycle – a phage reproductive cycle that results in the death of the host cell. Lysogenic cycle – replicates the phage genome without destroying the host. However, the virus is capable of entering the lytic cycle. Thought Question: After you have contracted chicken pox, the virus resides in your spinal cord. Later, the virus can re-emerge to cause shingles, a disease related to chicken pox. Explain this relationship in the context of viral reproduction.

Common Diseases Caused by Viruses Type of Virus Nucleic Acid Disease Oncogenic viruses Retroviruses Adenoviruses Herpesviruses Poxviruses DNA RNA cancer cancer, AIDS respiratory infections chickenpox smallpox

Essays After completing the microbe zoo activity you see one of your friends eating yogurt. Feeling all smart you point out to him that his cup of yogurt contains lactobacillus acidophillus, a type of bacteria. Your friend freaks out a little, throws the yogurt into the trash and starts shouting "Is the Dannon Corporation Crazy! Are they trying to get everyone sick with the flu or something!" Explain to your friend the two major biological problems with his statement. Include the terms bacteria, mutualism, large intestine, lactobacillus, diarrhea, E. coli, vitamin K, viruses, influenza. In 1928, the first antibiotic, penicillin, was isolated for human use. However, now penicillin is hardly ever prescribed because it is far less effective than it was 75 years ago. Why is this the case? Use the following terms in your answer: population, fitness, variation, resistance, gene pool, adaptation, mutation, environment.