Bacterial Cell Structure PDF

Bacterial Cell Structure Part 2 Section 2.6-2.8 pp 51-57; Section 7.5 pp 209-210 Figure 2.22 Biomineralization by a cyanobacterium Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Fts Proteins and Cell Division Prokaryote membranes are involved in repl...

Bacterial Cell Structure Part 2 Section 2.6-2.8 pp 51-57; Section 7.5 pp 209-210 Figure 2.22 Biomineralization by a cyanobacterium Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Fts Proteins and Cell Division Prokaryote membranes are involved in replication Fts (filamentous temperature-sensitive) proteins –Essential for cell division in all prokaryotes –Interact to form the divisome (cell division apparatus) FtsZ: forms ring around center of cell; it has been found to have structural homology to tubulin in eukaryotes ZipA: anchor that connects FtsZ ring to cytoplasmic membrane FtsI is a peptidoglycan biosynthesis protein, FtsK assists in chromosome separation, and FtsA is an ATPase Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 8.8 The FtsZ Ring and Cell Division Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 8.9 DNA Replication and Cell-Division Events MinCD inhibits formation of FtsZ ring MinE oscillates from pole to pole, sweeping MinCD aside When the cell becomes very long, there is little MinCD in the middle of the cell Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Determinants of Cell Morphology Prokaryotes can contain a simple cell cytoskeleton Crescentin: shape-determining protein found in curved cells organizes into filaments ~10 nm wide that localize on concave face of the curved cells MreB: major shape-determining factor in prokaryotes – Forms simple cytoskeleton with patchlike filaments around inside of cell just below cytoplasmic membrane in Bacteria and some Archaea – Not found in coccus-shaped bacteria – recruits other proteins for cell wall growth to group into a specific pattern Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 8.10 MreB and Crescentin as Determinants of Cell Morphology Rod A and class A and B penicillin-binding proteins (aPBP and bPBP) coordinate to synthesize new peptidoglycan transpeptidase and transglycosylase Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved S-Layers of Archaea S-Layers – Common cell wall component among Archaea (and some bacteria) – Consist of a protein or glycoprotein monolayer – S-layers act as structural support (rigid), molecular sieves (semi-permeable), and to form a pseudo- periplasmic space Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 2.14 S-Layers Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Capsule/exopolysaccharide/glycocalyx/slime layer -attachment to surfaces and biofilm formation -protection from grazing/immune systems/antibiotics -protection from dessication Dunfield Figure 2.16 Bacterial Capsules and Slime Formation Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Flagellum /Flagella... Dunfield Figure 2.30 Bacterial Flagella Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Pili and fimbriae Dunfield Fimbriae and pili filamentous protein structures ~2–10 nm wide Fimbriae enable organisms to stick to surfaces or form pellicles (thin sheets of cells on a liquid surface). Pili are typically longer, thicker, and fewer (1 or a few) found per cell than fimbriae. Conjugative pili facilitate genetic exchange between cells (conjugation). Type IV pili adhere to host tissues and support twitching motility (e.g., Pseudomonas and Moraxella). Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 2.17 Fimbriae Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 2.18 Pili Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Inclusion Bodies 1. Carbon/energy storage polymers i. PHA (polyhydroxyalkanoates) – a family of lipids that include PHB (poly-beta-hydroxybutyric acid) ii. Glycogen 2. Polyphosphate granules – inorganic phosphate storage 3. Sulfur globules – elemental sulfur in periplasm can be oxidized to sulfate (SO42-) 4. Carbonate minerals – biomineralization of barium, strontium, and magnesium Dunfield Figure 2.20 Poly-β-Hydroxyalkanoates (PHAs) Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 2.21 Polyphosphate and Sulfur Storage Products Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Protein-bound compartments 1) chlorosomes 2) carboxysomes Dunfield  Figure 15.15 The Thermophilic Green Sulfur Bacterium Chlorobaculum tepidum Chlorosomes are light antennae, they allow the bacteria to grow at low light intensities: Bchl c, d, or e capture light and direct it to Bchl a in the Reaction Center (RC) where photosynthesis occurs In Chloroflexi (GNSB) and Chlorobi (GSB) Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Wikipedia –Some obligate chemolithotrophs and photolithotrophs possess special structures that house Calvin cycle enyzmes (carboxysomes) –RubisCO- is the key enzyme involved in CO2 fixation Figure 15.30 Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Gas vesicles -buoyancy regulators in some planktonic bacteria Dunfield Figure 2.23 Buoyant Cyanobacteria and Their Gas Vesicles Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Magnetosomes -magnetic iron oxides allow cell to undergo magnetotaxis: migration along magnetic field lines Dunfield Figure 2.24 Magnetotactic Bacteria and Magnetosomes Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Endospores Endospores – Highly differentiated cells resistant to heat, harsh chemicals, and radiation – “Dormant” stage of bacterial life cycle – Ideal for dispersal via wind, water, or animal gut – Only present in some Gram-positive bacteria, e.g., Bacillus and Clostridium – only formed when growth ceases due to lack of an essential nutrient such as carbon or nitrogen – can remain dormant for years but convert rapidly back to being vegetative cell Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 2.26 The Life Cycle of an Endospore-Forming Bacterium Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved 250-million-year old bacterium from halite? Vreeland, R.H., Rosenzweig, WD, and Powers, D.W., Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal. Nature 407:897-900, 2000. Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Internal membranes (phototrophic, nitrifying, and methanotrophic bacteria) -Membranes are usually connected to the cytoplasmic membrane so they are “invaginations” rather than separate compartments -Key enzymes for these bacteria are membrane-bound, so more membrane=more enzyme Dunfield Nitrifying bacteria Nitrification (lithotrophic oxidation of ammonia to nitrate) usually occurs as two separate reactions by different groups of bacteria –Ammonia oxidizers (e.g., Nitrosococcus) –Nitrite oxidizer (e.g., Nitrobacter) –Many species have internal membrane systems that house key enzymes in nitrification Ammonia monooxygenase: oxidizes NH3 to NH2OH Nitrite oxidase: oxidizes NO2- to NO3 - Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 15.25 Nitrifying Bacteria Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved Figure 15.11 Membrane Systems of Phototrophic Purple Bacteria as Revealed by Transmission Electron Microscopy Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved  Some Planctomycetes have other internal membrane structures such as the annamoxosome and a nucleoid Figure 16.46 Anammoxosome Fig 14.26 Copyright © 2021, 2018, 2015 Pearson Education, Inc. All Rights Reserved