Download
1 / 33
330 likes | 640 Vues
Chapter 27: Prokaryotes. Cutting Board (Eubacteria). What are Prokaryotes?. See text for a better look at these, but no need to memorize these or associated information. Morphological Diversity. Common Bacterial Shapes. Spirochete. Cyanobacteria (blue-green algae).
E N D
See text for a better look at these, but no need to memorize these or associated information Morphological Diversity
Cyanobacteria (blue-green algae) Cyanobacteria are oxygen-liberating photosynthetic bacteria
Bacterial Cell Walls Peptidoglycan is material making up bacterial cell wall Thinner peptydoglycan layer and outer membrane Thicker peptydoglycan layer but no outer membrane
Bacterial Cell Walls “In a hypertonic environment, most prokaryotes lose water and shrink away form their cell walls (plasmolyze), like other walled cells. Severe water loss inhibits the reproduction of prokaryotes, which explains why salt can be used to preserve certain foods, such as pork and fish.”pp. 534-5, Campbell & Reece (2005) “One of the most important features of nearly all prokaryotic cells is their cell wall which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment.”p. 534, Campbell & Reece (2005)
Gram Stain Pink are Gram negative Purple are Gram positive
Bacterial Capsule Capsules provide desiccation resistance, attachment to surfaces, and resistance to phagocytosis
Bacterial Fimbriae Fibriae are involve in bacterial attachment to surfaces and resistance to phagocytosis
Conjugation Sex pili effect the transfer of conjugative plasmids
Flagella effect motility Bacterial Flagella Movement can be down or up concentration gradients, e.g., toward food
Invaginated Plasma membranes Some prokaryotes display invaginated plasma membranes This increases membrane area, just as seen, e.g., in mitochondria
Some bacteria can form endospores, which are non-replicative cell forms that are highly resistant to environmental insult Endospores
Biofilms Surface coating colonies of bacteria (often of more than one type) are called biofilms
Obligate aerobes require a functioning electron transport chain to grow, with O2 as a typical final electron acceptor • Key is their obligate use of an ETS to make ATP • Also key is their ability grow in the presence of oxygen (O2) • Facultative anaerobes can use O2 as a final electron acceptor for their electron transport chain (i.e., as aerobes), if available, but can grow using only fermentation (no ETS) if O2 is not available. • Obligate anaerobes cannot grow in the presence of O2 because they are poisoned by its presence • Some obligate anaerobes are obligate fermenters • Other obligate anaerobes are users of electron transport chains Bacterial O2 Requirements
Bacterial Nutrional Modes Know that outside parentheses
Together, bacterial species are very adept at metabolizing different forms of nitrogen, far more adept than are the sum of the eukaryotes • Nitrogen fixing is the conversion of atmospheric N (N2) into bioavailable N (e.g., NH3, ammonia) • Denitrification is the conversion of non-atmospheric N (nitrate and nitrite, NO3- and NO2-) to N2 (thus making the nitrogen no longer bioavailable except to nitrogen fixers) • The process by which denitrification occurs is known as anaerobic respiration, cellular respiration in which something other than O2 is reduced as the final electron acceptor • "In terms of nutrition, nitrogen-fixing cyanobacteria are the most self-sufficient of all organisms. They require only light, CO2, N2, water, and some minerals to grow.” p. 539, Campbell & Reece (2005) Nitrogen Metabolism
Specialized N2-Fixing Cells Nitrogen-fixing cyanobacteria
Archaea are unusual in terms of the environments in which they live, the substrates they consume, and the products they release • Included among Archaea are various extremophiles: • Extreme halophiles, organisms which live in extremely salty environments such as inland seas • Extreme thermophiles, organisms which live in hot springs and deep-sea hydrothermal vents • Mathanogens, which live in anaerobic environments, release methane as a metabolic waste product, thus producing marsh gas and flatulence from cellulose consuming herbivores (e.g., cattle, termites) • Archaea are also found in less extreme environments but those species of Archaea have not been studied as extensively as Archaea that live in extreme environments Archaea
Symbioses are intimate, relatively long-term interaction between organisms • Typically at least one of the organisms (the symbiont) benefits from the relationship • We can classify symbioses in terms of the degree to which the other organism (e.g., the host) benefits or is harmed: • Commensalism: one organisms benefits while the other neither benefits nor is harmed • Mutualism: both organisms benefit • Parasitism: one organism is harmed by the symbiont (the parasite) • A number of bacterial species can enter into either Commensal, Mutual, or Parasitic relationships with eukaryotic organisms, such as animals Symbiosies
Example: Mutualism It is mutualistic bacteria that produce the glow in these fish
Bacterial parasites typically have some means by which they can harm the host organism, such as by producing toxins • Toxins are chemical (often protein) agents that damage host tissue • Endotoxin is the Lipid A portion of LPS (not a protein) which causes host overreaction • Endotoxin is produced by Gram-negative bacteria • Exotoxins are protein toxins, typically produced by Gram-positives as exoenzymes or equivalents • But also many Gram-negatives • Examples include Neurotoxins and Enterotoxins Toxins
