LEC 5

• Prokaryotes are categorized into two domains: Archaea and Bacteria, with distinct characteristics and evolutionary backgrounds
• Each domain is organized into a hierarchy from phyla down to species, facilitating detailed classification and study
• Bacteria are further classified based on their cell wall composition using Gram staining, distinguishing them into gram-positive and gram-negative
• Contrary to common belief, only a minority of bacterial species are harmful, with many playing crucial roles in sustaining life on Earth
• Bacteria are essential for ecological balance and have significant roles in medicine, agriculture, and biotechnology
• Proteobacteria, primarily chemoheterotrophic, are believed to have evolved from a common photosynthetic ancestor
• Proteobacteria are divided into five classes (alpha, beta, gamma, delta, epsilon), demonstrating a wide range of metabolic diversity
• Alphaproteobacteria are capable of growth in low-nutrient environments, showcasing their adaptability and ecological importance
• Alphaproteobacteria include nitrogen-fixing bacteria in symbiosis with plants, and pathogens affecting both plants and humans
• Pelagibacter is one of the most abundant organisms on Earth, thriving in ocean environments with a minimal genome for survival in low-nutrient conditions
• Azospirillum is a soil bacterium associated with the roots of many plants, especially tropical grasses, playing a key role in nitrogen fixation
• Betaproteobacteria are characterized by diverse metabolic activities, including nitrogen cycling, important for environmental nutrient cycling
• Gammaproteobacteria include a wide range of organisms, from sulfur bacteria to pathogens, demonstrating the vast diversity within Proteobacteria
• Acetobacter and Gluconobacter are known for converting ethanol into acetic acid, a key process in vinegar production
• Granulibacter, a newly identified member of the Acetobacteraceae family, is linked to chronic granulomatous disease, showing the family's diverse impact on health
• Rickettsia reproduce only within mammalian cells, making them unique among bacteria
• Rickettsia are primarily transmitted to humans via insect and tick bites, highlighting their epidemiological significance
• Caulobacter species thrive in low-nutrient aquatic environments, using stalks for anchorage to surfaces, enhancing nutrient uptake
• Prosthecae are elongated, stalk-like structures that extend from the cell body, found in both Caulobacter and Hyphomicrobium
• Nitrosomonas oxidizes ammonium to nitrite, which Nitrobacter further oxidizes to nitrates, a crucial process for soil fertility and plant nutrition
• Rhizobium and Bradyrhizobium infect roots of leguminous plants, leading to nodule formation and symbiotic nitrogen fixation
• Agrobacterium tumefaciens causes crown gall disease by inserting a plasmid into the plant's DNA, leading to tumor formation
• Wolbachia live exclusively inside the cells of their hosts, usually insects, in a symbiotic relationship
• Betaproteobacteria use nutrients from anaerobic decomposition like hydrogen gas, ammonia, and methane
• Spirillum, found mainly in freshwater, is characterized by its motility through polar flagella
• Sphaerotilus natans form protective, filamentous sheaths in freshwater and sewage environments, aiding in nutrient accumulation
• Burkholderia cepacia is noted for its relevance in hospital contamination and cystic fibrosis
• Bordetella pertussis, a nonmotile, aerobic, gram-negative rod, is the pathogen causing whooping cough
• Neisseria species are aerobic, gram-negative cocci inhabiting mucous membranes
• Zoogloea bacteria are important in aerobic sewage-treatment processes, forming slimy masses essential for the activated sludge system's operation
• Thiomargarita namibiensis is the largest known bacterium in the Order Thiotrichales
• Pseudomonas aeruginosa is known for its pathogenicity and ability to produce distinctive pigments in the Order Pseudomonadales
• Legionella is associated with legionellosis, and Coxiella burnetii is the causative agent of Q fever in the Order Legionellales
• Vibrio cholerae is a key pathogen causing cholera in the Order Vibrionales
• Enterobacteriales bacteria inhabit the intestinal tracts of animals and humans, playing critical roles in health and disease
• Azotobacter and Azomonas are free-living nitrogen-fixing bacteria found in soil, known for converting atmospheric nitrogen into forms usable by plants
• Moraxella lacunata is notably implicated in conjunctivitis
• Moraxella, a strictly aerobic coccobacilli, is implicated in conjunctivitis, forming a strong reciprocal emotional bond between an infant and a primary caregiver
• Conjunctivitis, also known as pink eye, is an inflammation of the conjunctiva resulting in redness, itching, and discharge
• Understanding the pathogenic mechanisms of Moraxella lacunata is crucial for developing effective treatments and preventive measures against conjunctivitis