Review 1: Cytoplasmic Membrane and Transport PDF

GROUP 1 | CYTOPLASMIC prevalent in hyperthermophilic Archaea. MEMBRANE AND Lipids can have unique structures, TRANSPORT such as crenarchae...

GROUP 1 | CYTOPLASMIC prevalent in hyperthermophilic Archaea. MEMBRANE AND Lipids can have unique structures, TRANSPORT such as crenarchaeol, which Membrane Structure contains cyclopentyl and cyclohexyl rings. Cytoplasmic membrane serves as a barrier, maintaining selective Membrane Function permeability between the cytoplasm and the environment. Maintains cell integrity, supports Composed of a phospholipid bilayer, selective permeability, anchors approximately 8-10 nanometers proteins, and conserves energy. wide, visible under a transmission Functions as a barrier between electron microscope. cytoplasm and external environment, Contains common fatty acids with 14 regulating what enters and exits the to 20 carbon atoms, providing cell. structure. Appears somewhat rigid in Membrane Permeability diagrams, but is fluid like low-viscosity oil due to its lipid The cytoplasmic membrane nature. prevents unrestricted diffusion of Hopanoids, sterol-like compounds, substances, acting as a selective enhance the stability of bacterial barrier. membranes. Water passes freely due to its size; aquaporins facilitate rapid water Membrane Proteins transport. Larger molecules require specific Proteins span the membrane with transport proteins to cross the hydrophobic regions embedded and membrane. hydrophilic regions interacting with the environment and cytoplasm. Transport Proteins Integral proteins are firmly embedded in the membrane; Transport proteins are essential for peripheral proteins interact with moving molecules that cannot integral proteins and play roles in diffuse easily through the cellular processes. membrane. Lipoproteins anchor proteins into the Channel proteins create hydrophilic membrane, aiding in signal pathways for water and small, polar transduction and other cellular ions. functions. Carrier proteins transport substances across membranes and Archaeal Membranes can be found in both plasma and organelle membranes. Archaea feature membranes with phytanyl groups, utilizing ether Nutrient Transport bonds instead of ester linkages found in bacterial membranes. Cell transport systems are vital for Archaeal lipids may form lipid acquiring molecules necessary for monolayers or bilayers; monolayers growth and metabolism. are highly resistant to heat and  Three classes of transport systems Gram-Positive vs. Gram-Negative include simple transport, group Bacteria translocation, and ABC transport systems. Gram-positive bacteria have a thick, Transport events can occur through multi-layered peptidoglycan wall and unidirectional (uniport), simultaneous contain teichoic acids, contributing to (symport), or dual-directional their structural strength. (antiport) methods. Gram-negative bacteria possess a thinner peptidoglycan layer and have Simple Transport and Group an outer membrane that includes Translocation lipopolysaccharides (LPS). Simple transport relies on a Lipopolysaccharide (LPS) membrane-spanning protein and is Composition driven by proton motive force. Group translocation, such as the LPS consists of Lipid A, a core phosphotransferase system (PTS), polysaccharide, and O-specific chemically modifies substances polysaccharide (O-antigen). during transport using energy-rich Lipid A anchors LPS to the outer organic compounds. membrane of Gram-negative bacteria, with core polysaccharides Periplasmic Binding Proteins and linking it to O-antigens. ABC Transport System Periplasm and Porins Periplasm is the space between cytoplasmic and outer membranes in The periplasm is the gel-like space Gram-negative bacteria, containing between the inner and outer various transport proteins. membranes of Gram-negative ABC transport systems consist of bacteria, filled with enzymes and periplasmic binding proteins, proteins. membrane transporters, and Porins are specialized proteins in the ATP-hydrolyzing proteins to outer membrane that allow passage transport substances efficiently of small molecules and nutrients into across the membrane. the periplasm; they can be specific The structural feature of ATP-binding or nonspecific. ensures energy availability for transport processes. Gram Staining Process GROUP 2 | CELL WALLS OF Crystal violet serves as the primary BACTERIA AND ARCHAEA stain, followed by iodine treatment, and alcohol for decolorization; safranin is used as a counterstain. Peptidoglycan Structure Thick peptidoglycan in Gram-positive bacteria retains Peptidoglycan is a polymer made crystal violet, appearing purple; from alternating units of Gram-negative bacteria lose the N-acetylglucosamine (NAG) and violet stain and take up the N-acetylmuramic acid (NAM). counterstain, appearing pink or red. Provides structural integrity, rigidity, and shape to bacterial cells. Archaeal Cell Walls Pili occur only in Gram-negative bacteria, with 1-4 present per cell. Archaea may feature pseudomurein, Pili are longer and broader than which includes N-acetylglucosamine fimbriae and are involved in and N-acetyltalosaminuronic acid conjugation processes, controlled by (replacing N-acetylmuramic acid). the fertility factor (F+). Pseudomurein's glycosidic bonds differ (β(1→3) versus β(1→4) in Polyphosphate and Cellular peptidoglycan) and vary in Processes stereochemistry. Polyphosphate granules serve dual S-Layers purposes: energy storage and phosphate storage. Archaea commonly have an S-layer, Degraded polyphosphate is a paracrystalline layer of interlocking converted into nucleotide proteins or glycoproteins that can triphosphate (ATP). withstand osmotic pressures. Sulfur within cells comes from The S-layer serves as the outermost reduced sulfur sources; when wall layer, acting as a selective sieve limited, sulfur granules may be that retains proteins close to the cell oxidized to sulfate. surface. Certain cyanobacteria, like Gleomargarita, form carbonate GROUP 3 | OTHER CELL minerals such as benstonite on surfaces, with some forming them SURFACE AND INCLUSIONS intracellularly. Structure and Function of Functions of Polyphosphate, Glycocalyx Sulfur, and Carbonate Glycocalyx is a thin deformed layer Polyphosphate acts as a precursor surrounding the bacterial cell wall. for ATP production, aiding in Functions include cell binding, phosphate storage and future nutrient trapping, surface adhesion, conversion. and protection against desiccation. Sulfur is crucial for energy Staphylococcus species are known metabolism (chemolithotrophy) and to form slime layers, contributing to CO2 fixation (autotrophy) within biofilm development. cells. Carbonate plays a role in Fimbriae and Pili biomineralization, a process catalyzed by various prokaryotes, Fimbriae are found in both stabilizing cellular environments and Gram-positive and Gram-negative aiding habitat maintenance. bacteria. Typically, 300-400 fimbriae are Structure and Function of present per cell, characterized by their shorter and narrower structure. Bacterial Layers Primarily involved in adhesion Glycocalyx forms a thin deformed formation, regulated by nucleoid layer around the bacterial cell wall. gene expression.  Functions include binding to cells, Functions of Polyphosphate, trapping nutrients, adhering to Sulfur, and Carbonate surfaces, and protecting against desiccation. Polyphosphate aids in ATP Staphylococcus species are known synthesis, enabling phosphate to form slime layers. storage and energy production. Sulfur plays critical roles in energy Biofilms metabolism (chemolithotrophy) and carbon fixation (autotrophy). Biofilms consist of communities of Carbonate is significant for bacteria encased in a protective biomineralization, helping stabilize layer, enhancing survival and cells in their environments. resistance. GROUP 4 | MICROBIAL Fimbriae vs. Pili LOCOMOTION Fimbriae are found in both Gram-positive and Gram-negative Introduction to Microbial bacteria; pili are exclusive to Locomotion Gram-negative bacteria. Motility enables prokaryotic cells to Average of 300-400 fimbriae per navigate their environments. cell, whereas pili number ranges Major prokaryotic cell movement from 1-4 per cell. types include swimming and gliding. Fimbriae are shorter and narrower; pili are longer and broader. Swimming Motility Fimbriae facilitate adhesion; pili are Flagella, measuring 15-20 nm, involved in bacterial conjugation. facilitates swimming motility in Fimbriae formation is influenced by bacteria. nucleoid gene expression; pili formation is controlled by the fertility Types of Flagellation factor (F+). Polar Flagellation: Flagella attached at one or both ends of a cell. Polyphosphate and Sulfur Peritrichous Flagellation: Flagella Processes dispersed over the entire surface of the cell. Polyphosphate granules serve varied roles, including energy and Flagellar Structure phosphate storage, and are Flagella are helical with a consistent degraded to produce ATP. wavelength. Sulfur primarily sourced from reduced sulfur; limited supply Components include: prompts oxidation of granule sulfur Tip to sulfate. Filament Carbonate minerals, like benstonite, Hook form on filamentous cyanobacteria Motor: Comprising L, P, MS, such as Gleomargarita, with some and C Rings. forming minerals intracellularly. Mot proteins Fli proteins Flagellar Movement Functions as a rotary motor allowing Chemotaxis circular movement. Directed movement in response to Structure includes rotor (central rod chemical stimuli. and rings) and stator (mot proteins). Movement powered by the bacterial Differences in Chemotaxis proton motive force. Peritrichous Flagellated Bacteria: Exhibit runs (forward swimming) and Archaeal Flagella tumbles (stopping and jiggles). Have a width of 10-13 nm. Polar Flagellated Bacteria: Can reverse flagella rotation to change Composed of various flagellin movement direction. proteins and powered directly by ATP. Measuring Chemotaxis Flagellar Synthesis Capillary Tube Assay: Begins with assembly of MS and C Controlled: No change in rings in the cytoplasmic membrane. microorganism movement. Flagellin flows through the hook to Attractant: Microorganisms form the filament; guided by cap swarm towards chemical. proteins. Repellent: Microorganisms move away from chemical. Speed and Motion Influences Phototaxis Speed and movement direction True Phototaxis: Movement towards depend on flagella type and increasing light intensity. arrangement. Scotophobotaxis: Random Polar Flagella: Result in slow and swimming out of illuminated areas linear swimming. under a microscope. Peritrichous Flagella: Cause erratic or tumbling swimming patterns. Other Types of Taxes Aerotaxis: Movement towards or Mechanisms of Gliding Motility away from oxygen. Rod-shaped bacteria can glide Osmotaxis: Movement influenced by without flagella, cilia, or pili. ion concentration. Hydrotaxis: Movement towards or Gliding Mechanisms away from water. Slime Extrusion: Secretion of a slimy substance for propulsion. Type IV Pili Mechanism: Involves retraction and extension of pili (e.g., Pseudomonas aeruginosa). Protein Adhesion Complex: Forms a sticky adhesion allowing movement (e.g., Myxococcus xanthus). Surface Protein Movement: Uses gliding-specific proteins for forward motion (e.g., Flavobacterium).