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A comprehensive overview of the internal and external structures of bacteria, including the plasma membrane, cell wall, and various organelles and appendages. It delves into the functions of these structures, such as nutrient uptake, waste elimination, and motility. The document also discusses the differences between gram-positive and gram-negative bacteria, highlighting the unique features of their cell envelopes. Additionally, it covers the importance of macronutrients, micronutrients, and growth factors in bacterial growth and metabolism. The information presented in this document is highly relevant for understanding the fundamental biology of prokaryotic cells and their adaptations to various environments.
Typology: Exercises
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Are bacteria prokaryotes or eukaryotes? prokaryotes Prokaryotes Bacteria and Archaea, lack organelles Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0: / 0: Full screen Brainpower Read More coccus round diplococcus pairs staphylococcus
cluster of cocci streptococcus chain of cocci sarcina coccus a group of eight coccus cells, cube shaped tetrad coccus a group of four coccus cells bacillus Rod shaped bacteria coccobacillus short round rod diplobacillus double bacillus streptobacillus chain of rods palisades cells of a chain remain partially attached and fold back, creating a side-by-side row of cells vibrio comma shaped bacteria spirillum spiral shaped bacteria helical form rod-shaped capsomeres bond together to form helix spirochete spiral shaped bacteria (longer than spirillum) hypha and stalk A filament of fungal cells. pleomorphic
Plasma membrane structure is dynamic Amphipathic lipids polar ends (hydrophilic - interact with water) non-polar tails (hydrophobic - insoluble in water and interact with each other) two types of membrane proteins integral proteins and peripheral proteins peripheral membrane proteins loosely connected to the membrane and easily removed (20-30% of the total membrane proteins) integral membrane proteins amphipathic proteins that are embedded within membrane and not easily removed (hydrophobic and hydrophilic regions) the plasma membrane is mainly composed of phospholipids hopanoids hydrophobic molecule similar to cholesterol, distorts the bilayer, which impacts the fluidity and shape in membrane region, form functional membrane microdomains that are platforms for protein complex assembly macronutrients required in large amounts, found in organic molecules (proteins, lipids, nucleic acids, and carbs) cations contribute to
activity and stability of molecules and cell structures, important in cellular processes (protein synthesis) micronutrients required in small amounts, ubiquitous in nature and usually present in adequate amounts to support microbial growth, work to assist enzyme catalysis and maintain protein structure macronutrient examples carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus cationic macronutrients potassium, calcium, magnesium, iron micronutrient examples manganese, zinc, cobalt, molybdenum, nickel, and copper growth factors amino acids, purines, pyrimidines, and vitamins siderophores secreted by bacteria and complex with ferric ion for transport into cell, iron uptake cell wall functions maintains shape of the bacterium, helps protect cell from osmotic lysis and toxic materials, and may contribute to pathogenicity peptidoglycan (murein) rigid structure lying outside the plasma membrane, apart of cell wall in prokaryotes gram-positive
between plasma membrane and cell wall, periplasm has few proteins gram-negative cell wall thin layer of peptidoglycan and an outer membrane, NO TEICHOIC ACID outer membrane of gram-negative bacteria is composed of lipopolysaccharides Braun's lipoproteins connect outer membrane to peptidoglycan 3 parts of lipopolysaccharides:
Hypotonic environment solute concentration outside the cell is less than inside the cell, water moves into cell and cell swell, cell wall protects from lysis Hypertonic environment solute concentration outside the cell is greater than the inside, water leaves cell and cytoplasm shrivels up (plasmolysis) lysozyme enzyme that breaks bond between NAG and NAM protoplast and spheroplast gram-positive cells that lose cell wall in isotonic environments mycoplasma lack a cell wall, but plasma membrane more resistant to osmotic pressure extracellular vesicles -small membrane-bound particles (20 to 400 nm in size) -develop when a membrane buds out, pinches off, and is released from the cell
bacterial cytoplasmic structures cytoskeleton, intracytoplasmic membranes, inclusions, ribosomes, nucleoid, and plasmids protoplast plasma membrane and everything within cytoplasm material bounded by the plasma membrane cytoskeleton protein filaments that polymerize to form functional filaments that extend to full inner dimensions of the cell homologs of eukaryotic cytoskeleton elements in bacteria actin filaments, microtubules, and intermediate filaments cytoskeleton functions participate in cell division, localize proteins, and maintain cell shape bacterial cytoskeleton molecules FtsZ, MreB, CreS intracytoplasmic membranes
components so they do not diffuse freely in the cytoplasm
sex pili -longer, thicker, and less numerous (10/cell) -genetically on plasmids -required for conjugation flagella threadlike, locomotor appendages extending outward from plasma membrane and cell wall flagella functions motility, attachment to surfaces, and virulence factors patterns of flagella distribution monotrichous - one flagellum polar flagellum - flagellum at end of cell amphitrichous - one flagellum at each end of cell lophotrichous - cluster of flagella at one or both ends peritrichous - spread over entire surface of cell bacterial flagella Thin, rigid protein structures that cannot be observed with bright-field microscope unless specially stained Ultrastructure of flagella 3 parts: filament- extends from cell surface to the tip basal body- embedded in cell envelope hook- short curved segment flagella synthesis -complex process involving many proteins -new flagellin molecules transported through the hollow filament
-filament subunits self-assemble with help of filament cap at tip, not base flagellar movement: swimming, swarming, spirochete motility, twitching and gliding motility, and chemotaxis swimming flagella
gamma radiation, chemicals disinfectants, and desiccation endospore structure -spore surrounded by thin covering called exosporium -thick layers of protein form the spore coat -cortex, beneath the coat, thick peptidoglycan -core has nucleoid and ribosomes sporulation
