8_28 Fundamentals III more structures start growth.pptx

Structure continued and growth Read Chapter on growth Figure 4.13b Bacterial cell walls. Figure 4.13c Bacterial cell walls. O polysaccharide Core...

Structure continued and growth Read Chapter on growth Figure 4.13b Bacterial cell walls. Figure 4.13c Bacterial cell walls. O polysaccharide Core polysaccharide Core polysaccharide Lipid A Lipopolysaccharide O polysaccharide Parts of the LPS Lipid A Porin protein Lipoprotein Phospholipid Outer membrane Cell wall Peptidoglycan Plasma membrane Periplasm Protein  Atypical Cell Walls Acid-fast cell walls – Like gram-positive cell walls – Waxy lipid (mycolic acid) bound to peptidoglycan – Mycobacterium – Nocardia Figure 24.8 Mycobacterium tuberculosis.  More Atypical Cell Walls Mycoplasmas – Lack cell walls – Sterols in plasma membrane Archaea – Wall-less, or – Walls of pseudomurein (lack NAM and D- amino acids)  Figure 4.6 The Structure of a Prokaryotic Cell. The drawing below and the Cell wall micrograph at right show a bacterium Capsule sectioned lengthwise to reveal the Although the nucleoid appears Pilus internal composition. Not all bacteria split in the photomicrograph, have all the structures shown; only the thinness of the “slice” does structures labeled in red are found in not convey theobject’s depth. all bacteria. Cytoplasm 70S Ribosomes Plasma membrane Nucleoid containing DNA Inclusions Plasmid Fimbriae Capsule Cell wall Plasma membrane Flagella © 2013 Pearson Education, Inc..  Inclusions Metachromatic granules (volutin)—phosphate reserves Polysaccharide granules—energy reserves Lipid inclusions—energy reserves Sulfur granules—energy reserves Carboxysomes—Ribulose 1,5-diphosphate carboxylase for CO2 fixation Gas vacuoles—protein-covered cylinders Magnetosomes—iron oxide (destroys H2O2)  Endospores Resting cells Resistant to desiccation, heat, chemicals Bacillus, Clostridium Sporulation: endospore formation Germination: return to vegetative state Figure 4.21b Formation of endospores by sporulation. Endospore An endospore of Bacillus subtilis Figure 4.21 - Overview Table 4.2 (1 of 2) Table 4.2 (2 of 2)  Bacterial Growth Read Chapter 5, we will come back to Chapters 3 and 4 (This will make your first test easier…)  Growth Multiple methods to measure growth Volume Size (height and width) Number of cells – Most important for Bacteria  Principles of Bacterial Growth Prokaryotic cells divide: – binary fission – One cell divides into two Two into four etc. – Cell growth is exponential Doubling of population with each cell division Exponential growth has important health consequences – Generation time Time it takes for population to double a.k.a doubling time Varies among species  Principles of Bacterial Growth Number of bacteria can be calculated based on exponential growth equation Nt = N0 x 2n (Nt ) number of cells in population (N0 ) original number of cells in the population (n) number of divisions For Example If a bacterium has a generation time of 20 minutes, after 4 hours how many bacteria will be present? N0 = 10 cells in original population from a finger n = 12 cell divisions or generations Nt = 10 x 212 Nt = 10 x 4,096 Nt = 40,960 (from 10 cells after 4 hours…..) (68,719,476,736 after 12 hours…) Figure 6.12a Figure 6.13  Triggers for Cell division Most cells in culture are similar size – Size homeostasis Two historical theories – Timer vs sizer – Age structured vs size structured population Size of bacteria at birth correlates with size at cell division (small make smaller, larger make larger) – May be more than just size? BMC Biology 2014 12:17 DOI: 10.1186/1741-7007-12-17 Scientific Reports 6, Article number: 30229 (2016) doi:10.1038  Cell division Cells reach critical size – Triggers cell division – “Adder Principal” Cells add a fixed volume Scientific Reports 6, Article number: 30229 (2016) doi:10.1038  Prokaryotic Cell Cycle B = “Birth” immediately after cell division (before replication) C= Period of chromosome replication (analogous to “S” phase) D = Period after completion of replication and completion of cell division Nat Rev Microbiol. 2009 November ; 7(11): 822–827  Figure 1. The bacterial cell cycle. The bacterial cell cycle can be divided into three stages: B, C and D. (a) The B... FEMS Microbiol Rev, Volume 42, Issue 2, March 2018, Pages 116–136, https://doi.org/10.1093/femsre/fuy005 The content of this slide may be subject to copyright: please see the slide notes for details.  Divisome Coordinates – Cell division – chromosome replication – Fts proteins Fts proteins form a division apparatus called divisome. (Filament temperature sensitive-prokaryotic equivalent to tubulin)  FtsZ ring Regulated by carbon availability and intracellular UDP-glucose (peptidoglycan precursors) Nat Rev Microbiol. 2009 November ; 7(11): 822–827  Models for division-site selection in E. coli (Left) and B. subtilis (Right). Christine Jacobs, and Lucy Shapiro PNAS 1999;96:5891- 5893 ©1999 by National Academy of Sciences Peptidoglycan fills in gap  Why is this critical? Autolysis – without new wall Drugs prevent cell wall formation –Penicillin and its derivatives Many drugs block synthesis not degrade cell wall  One Minute Summary Write a one minute review of bacterial growth – How do they divide – Result of this division – Critical step