Bacteria and Archaea fall 2024 (2).pdf

BIO 202 – Bacteria and Viruses Figure 25.16 25.5 Horizontal Gene Transfer  Horizontal Gene Transfer - Any process in which an organism incorporates genetic material from another organism without being the offspring of that organism – Contrasts with vertical gene...

BIO 202 – Bacteria and Viruses Figure 25.16 25.5 Horizontal Gene Transfer  Horizontal Gene Transfer - Any process in which an organism incorporates genetic material from another organism without being the offspring of that organism – Contrasts with vertical gene transfer from parent to progeny Increases genetic diversity Common among archaea and bacteria (prokaryotes) Can result in large genetic changes 25.5 Horizontal Gene Transfer; 27.1 Diversity and Evolution  Prokaryotes v eukaryotes Prokaryotes – bacteria and archaea Prokaryotes do not have bound organelles Eukaryotes – organisms with bound organelles – Organelles –subcellular structures that perform the different required functions of the eukaryotic cell Chloroplasts – plastid that conducts photosynthesis Mitochondria plastid that conducts respiration - the process in which nutrients are converted into useful energy in a cell 27.1 Diversity and Evolution Figure 4.8 Figure 4.11 Figure 27.1 Prokaryotes are paraphyletic 27.1 Diversity and Evolution  Figure 27.2 Bacteria have Peptidoglycan (Polymer that helps maintain shape) in their cell walls and an outer envelope (contact with the environment, protection). Archaea do not. 27.1 Diversity and Evolution  Domain Archaea Features in common with the eukaryotic nucleus and archaea suggesting common ancestry Histone proteins, Ribosomal proteins, RNA polymerases Unique membrane lipids give resilience Ether-bonded lipids more resistant to heat and other conditions Allow Archaea to live in extreme environments Extremophiles – organisms that are capable of living in harsh environments (e.g., high salinity, high temperatures) – Many Archaea are found in moderate conditions as well 27.1 Diversity and Evolution  Domain Bacteria ~50 bacterial phyla Structural and metabolic features of half are still unknown Most bacteria favor moderate conditions However, some bacteria are extremophiles Many form symbiotic relationships with eukaryotes 27.1 Diversity and Evolution  Fig. 27.3 Phylum Cyanobacteria Can be found in freshwater and marine environments. Can form a mutualistic relationship with fungi to make Lichens Capable of aerobic photosynthesis: 6 CO2 + 12 H2O -> C6H12O6 +6O2+6H2O Water provides electrons – Oxygen is a byproduct 27.1 Diversity and Evolution. The Cyanobacteria and the great oxygenation event – Over 3 billion years ago, cyanobacteria produced oxygen as by- product of photosynthesis. – Oxygen accumulated in atmosphere, becoming substantial 1 billion years ago. – As oxygen accumulated, other photosynthetic organisms appeared and forms of aerobic respiration developed. – In last half billion years enough ozone for UV shield and for photosynthetic organisms to survive on land. Stage 1: Practically no O2 in the atmosphere. Stage 2: O2 produced, but absorbed in oceans & seabed rock. Stage 3: O2 starts to gas out of the oceans, but is absorbed by land surfaces. Stages 4 & 5: O2 sinks filled and the gas accumulates. The GOE almost killed all life: https://thewonderofscience.com/phenomenon/2018/6/15/the-great-oxygenation-event  Fig. 27.5 Bacteria and archaea share small size, rapid growth, and simple cellular structure Bacteria and archaea are just 1–5 μm in diameter Most plant and animal cells are between 10 and 100 μm in diameter Small cell size limits the amount of materials in a cell but allows faster cell division Thylakoids – ingrowths of plasma membrane that increase surface area for photosynthesis Chlorophyll – pigment that absorbs light energy in photosynthesis Gas vesicles to adjust buoyancy Nucleus-like bodies from plasma membrane invaginations 27.2 Structure and Movement  Magnetosomes – magnetite crystals – Like a compass – Helps to locate low-oxygen habitats Fig. 27.6 - complexity 27.2 Structure and Movement  Five major shapes 1. Spheres – cocci 2. Rods – bacilli 3. Comma-shaped – vibrios 4. Spiral-shaped flexible – spirochaetes 5. Spiral-shaped rigid – spirilli Occur as single cells, pairs, or filaments Fig. 27.7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 μm 11.4 μm 15 μm 7.5 μm (a) Sphere-shaped cocci (b) Rod-shaped bacilli (c) Comma-shaped vibrios (d) Spiral-shaped spirochaetes (Lactococcus lactis) (Lactobacillus plantarum) (Vibrio cholerae) (Leptospira sp.) a: © SciMAT/Photo Researchers, Inc.; b-d: © Dennis Kunkel Microscopy 27.2 Structure and Movement  Fig. 27.8 Mucilage – thick substance consisting of sugars, proteins, fats, and nucleic acids Secreted from cells Functions: Movement Evade host defenses Hold colony together – biofilms - aggregations of microorganisms that secrete adhesive mucilage, gluing themselves to a surface 2.3 μm 27.2 Structure and Movement  Cell-wall structure Most have rigid cell wall outside the plasma membrane Maintain cell shape and help protect against attack Also help avoid lysis in hypotonic solutions Most bacteria use peptidoglycan as an important component of cell walls 27.2 Structure and Movement  Gram stain Gram positive Relatively thick peptidoglycan layer Purple dye held in thick layer Cells are stained purple Vulnerable to penicillin that interferes in cell wall synthesis Gram negative Less peptidoglycan and a thin outer envelope of lipopolysaccharides Lose purple stain but retain final pink stain Cells are stained pink Resists penicillin and requires other antibiotics 27.2 Structure and Movement Figure 27.9 27.2 Structure and Movement  Figure 27.10 Gram positive are typically more sensitive to antibiotics because antibiotics interfere with synthesis of peptidoglycan The lipopolysaccharide-rich outer envelope of Gram-negative bacteria helps them to resist the entry of some antibiotics. For fun: Waksman started cultivating soil bacteria in the 1930s for antibiotic discovery. Since then we’ve discovered all of the antibiotics of culturable bacteria. This is an interesting article about how a low tech approach from a previous house painter led to the discovery of 25 new antibiotics in 2015. https://www.statnews.com/20 15/12/03/antibiotics-bacteria- research/ 27.2 Structure and Movement  Motility Allows cells to move to favorable conditions Respond to chemical signals Swim with flagella, twitch (pili), glide or adjust flotation 27.2 Structure and Movement  Binary fission – divide by splitting in two Asexual reproduction Advantage: can lead to rapid increase in the number of individuals in the population. Plus, 100% of the genome gets to the offspring. Disadvantage: If environmental conditions change, there is little genetic variation for selection to operate on. Fig. 27.14 Copyright © The McG raw-Hill Compan ies, In c. Permission re quired for repro duction or display. 0.8 μm 39 μm (a) Bacterium undergoing binary fission (b) Colonies developed from single cells (c) Bacteria stained with fluorescent DNA-binding dye a: © Scientifica/RML/ Visuals Unlimited; b: © Michae l G abridge /Visuals Un limited; c : © Lee W. Wilcox Sexual reproduction Advantage: ensures there is genetic variation in the population. Selection can operate. Disadvantage: Energetically costly to attract and maintain a mate. Genetically costly, too, as a parent contributes only 50% of its genome to offspring. 27.3 Reproduction  Bacterial Chromosomes Molecules of double-stranded DNA, usually circular Fig 19.10 19.4 Genetic properties of bacteria  Plasmids Small, circular pieces of DNA that exist independently of the bacterial chromosome Own origin of replication that allows it to be replicated independently of the bacterial chromosome Not usually necessary for survival but can provide growth advantages 19.4 Genetic properties of bacteria  Five types of plasmids 1. Resistance plasmids (R factors) Confer resistance against antibiotics and other types of toxins 2. Degradative plasmids Enable the bacterium to digest and utilize an unusual substance 3. Col-plasmids Encode colicines, which are proteins that kill other bacteria 4. Virulence plasmids Turn a bacterium into a pathogenic strain 5. Fertility plasmids (F factors) Allow bacteria to mate 19.4 Genetic properties of bacteria  Genetic diversity from Table mutations or genetic 19.3 transfer: 1. Conjugation Direct physical interaction transfers genetic material from donor to recipient cell 2. Transformation DNA released from a dead bacterium into the environment is taken up by another bacteria 3. Transduction A virus transfers genetic information from one bacterium to another 19.4 Gene Transfer Between Bacteria  Surviving harsh conditions Akinetes Found in aquatic filamentous cyanobacteria Develop when winter approaches Survive winter and produce new filaments in spring Heterocyte – specialized cell that can convert atmospheric N into forms utilizable by photosynthetic organisms (N fixation) Endospores Tough protein coat Amazingly long dormant span Found in some Gram-positive bacteria Bacillus anthracis, Clostridium botulinum, Clostridium tetani 27.3 Reproduction Fig. 27.15 Copyright © The McG raw-Hill Compan ies, In c. Permission re quired for repro duction or display. Heterocyte Akinete Endospore 13 μm 0.3 μm (a)Cyanobacterial (b) Clostridium difficile akinete a: © Lee W. Wilcox; b: © Dr. Ka ri L ounatmaa/Photo Re sea rch ers, Inc. 27.3 Reproduction  Classification of Bacteria - nutrition Autotrophs – Produce all or most of their own organic compounds – Photoautotroph Uses light as energy source for synthesis of organic compounds from CO2 and H2O or H2S – Chemoautotrophs Use energy obtained from chemical modification of inorganic compounds to synthesize organic compounds Heterotrophs – uses organic carbon for growth by consuming other organisms 29 27.4 Nutrition and Metabolism  Symbiotic roles Symbiosis – An organism that lives in close association with one or more other organisms Parasitism – One partner benefits at the expense of the other Mutualism – Association is beneficial to both partners For fun: Video on anglerfish by internet humorist Zee Frank – mutualism with bioluminescent bacteria: https://www.youtube.com/watch?v=Z-BbpaNXbxg 27.5 Ecological Roles and Biotechnology Applications  Mutualisms with eukaryotes Diazotrophs – conduct nitrogen fixation converts inorganic nitrogen gas N2 into N compounds that plants can utilize Rhizobium and legumes Lichens – mutualism between cyanobacteria and fungi Lichen Rhizobium 27.5 Ecological Roles and Biotechnology Applications  As nature tends to utilize ingredients The human available in its midst to build, mould and customize its occupants, microbes were a natural choice for this bioengineering task. microbiome Hence, microbes became part of most if not all living organisms. They live as symbiotic partners, supply essential nutrients, act as guards and shape morphological and physiological attributes. Although the presence of microbes housed in specific locations in numerous organisms has been detected before, their beneficial interaction with humans has only recently begun to be appreciated. The discovery of new molecular visualization technologies is providing an unprecedented view of the intimate relationship humans have forged with https://link.springer.com/chapter/10.1007/9 microbial partners. In fact, the vast 78-981-10-7684-8_1 majority of cells we harbor are microbial in origin. The entirety of microbes living within and on us, referred to as the microbiome, is an integral part of 27.5 Ecological Roles and the human body, just like the visible Biotechnology Applications organs such as the heart and the eye.  Parasitism Pathogens – Organisms that obtain organic compounds from living hosts at the expense of the host – Examples Cholera, leprosy, tetanus, pneumonia, whooping cough, diphtheria, Lyme disease, scarlet fever, rheumatic fever, typhoid fever, bacterial dysentery, and tooth decay 27.5 Ecological Roles and Biotechnology Applications Gram-negative pathogenic Figure 27.18a bacteria developed needle-like systems, made of components also found in flagella, that inject proteins into animal or plant cells as part of the infection process. The bacterium induces the infected cell to enclose it in a plasma membrane and then it uses the infected cells resource to reproduce. 27.5 Ecological Roles and Biotechnology Applications  Figure 27.18b Gram-negative pathogenic bacteria developed channel that inject DNA into animal or plant cells as part of the infection process. Evolved from pili 27.5 Ecological Roles and Biotechnology Applications  Properties of Viruses Viruses and viroids are nonliving particles with nucleic acid genomes that require the assistance of living cells to reproduce Do not grow by increasing in size or dividing Do not respond to external stimuli Cannot move on their own Cannot carry on independent metabolism 19.1 Properties of viruses  Viruses Small infectious particle that consists of nucleic acid enclosed in a protein coat Over 4,000 different types Vary greatly in their characteristics 19.1 Properties of viruses Figure 19.2 18.1 Properties of viruses Viral structure 19.1 Properties of viruses  Reproduction Viral reproductive cycle can be quite different among types of viruses, we’ll focus on a basic type 19.2 Viral reproductive cycles  Viral Reproductive Cycle 1. Attachment 2. Entry 3. Integration 4. Synthesis of viral components 5. Viral assembly 6. Release 19.2 Viral reproductive cycles Figure 19.4a steps 1 through 3 19.2 Viral reproductive cycles Figure 19.4a steps 4 through 6 19.2 Viral reproductive cycles  Prions Prion converts normal proteins to abnormal form Composed entirely of protein Several types of neurodegenerative diseases of human and livestock Normal conformation PrP C Disease causing conformation PrP Sc 19.3 Prions Figure 19.8 19.3 Prions Table 19.2 19.3 Prions