Brock Biology of Microorganisms Chapter 2

morphology

cell shape

coccus

spherical or ovoid shape

bacillus

rod or cylindrical shape

spirillum

curved or spiral shape

spirochetes

tightly coiled shape, appendaged bacteria, and filamentous bacteria (includes budding bacteria)

size range for most prokaryotes

-0.2-->700 micrometers in diameter

-largest is Thiomargarita namibiensis

size range for eukaryotes

-2->>600 micrometers in diameter

advantages to being small

-larger surface area to cell volume ratio

-grow faster

-evolve faster

ultramicrobacteria

bacteria between 0.2-0.4 micrometers in diameter with highly streamlined genomes

bacterial cytoplasmic membrane

-membrane that is more like a matrix instead of a completely fixed structure (very fluid/dynamic)

-have phospholipid bilayer w/proteins

hopanoids

sterol-like molecules that help strengthen some bacterial cell walls

archaeal membranes

-have ether linkages in phospholipids of archaea (in contrast to ester links)

-lipids have isoprenes, not fatty acids

-some only have monolayer if lipids (not bilayer, especially in thermophilic)

bacterial cell walls

-these walls have peptidoglycan

mycoplasms

pathogenic bacteria related to gram-positive bacteria, but do not have cell walls

thermoplasmas

archaea that do not have cell walls

archaeal cell walls

-these walls do not have peptidoglycan

-many, but not all, have pseudomurein

pseudomurein

substance found in cell walls of certain methanogenic archaea; polysaccharide similar to peptidoglycan

-penicillin and lysozyme would not work on these

capsules and slime layers

-assist in surface attachment

-develop and maintain biofilms

-protect against phagocytosis

-prevent dehydration/dessication

fimbriae and pili

-filamentous protein structures

-help organisms stick to surfaces or form pellicles

hamus/hami

-archaeal "grappling hooks" help surface attachment, forming biofilms

-resemble pili except for barbed terminus

cell inclusions

not a true organelle, but help cells save materials for later if able

-energy reserves

-carbon reserves

-enclosed by thin membrane

-reduce osmotic stress

gas vesicles

-confer buoyancy in planktonic cells

-conical-shaped, gas-filled structures made of protein

-impermeable to water and solutes

composed of GvpA and GvpC

-function by decreasing cell density

endospores

-highly differentiated cells resistant to heat, harsh chemicals, and radiation

-present only in GRAM POSITIVE bacteria

-nearly 20 types

endospore life cycle

-vegetative cell converted to non-growing, heat-resistant, light-refractive structure due to lack of essential nutrients (C and N, etc)

-will beging growing again when conditions are met (triggered by signals due to genetics)

-Steps are ACTIVATION, GERMINATION, OUTGROWTH

endospore structure

-exosporium

-spore coats

-cortex

-core

-core wall (some)

endospore features

-contains dipicolinic acid

-enriched in Ca2+

-core has acid-soluble spore proteins that bind and protect DNA and function as carbon and energy source for outgrowth

sporulation cycle

complex series of events; for over 200+ sprore-specific genes

flagella/archaella

structure that assists in swimming in Bacteria and Archaea, respectively (tiny rotating machines)

polar flagella

one or more of this arising from one or both poles of a cell

lophotrichous flagella

Several flagella (tuft) can extend from one end or both ends of the cell

amphitrichous flagella

A single flagellum (or multiple flagella; see below) can extend from both ends of the cell

peritrichous flagella

Multiple flagella may be randomly distributed over the entire bacterial cell

synthesis of flagella

steps to synthesize ??:

(several genes required; filament grows from tip)

1) MS ring made first

2)other proteins and hook are made next

archaella specifics

-half diameter of bacterial flagella

-move by rotation

-have different filament proteins with little homology to bacterial flagelin

-similar to type IV pili

gliding motility

-this movement only executed by bacteria; not archaea

-slower and smoother than swimming

-movement typically occurs away from colong

-requires surface contact

-taxis

directed movement in response to chemical or physical gradients

chemotaxis

-response to chemicals

-exhibit "run and tumble" behavior

phototaxis

response to light

aerotaxis

response to oxygen

osmotaxis

response to ionic strength

hydrotaxis

response to water

chemoreceptors

these can sense attractants and repellants based on chemicals in an environment

measuring chemotaxis

this involves inserting a capillary tube containing an attractant or a repellant in a medium of motile bacteria and seeing where microbes gravitate

scotophobotaxis

response involving entering darkness, cells subsequently tumbling, reversing direction, and heading back toward light

nucleus

-contains the chromosomes

-DNA wound around histones

-enclosed by two membranes that interact with nucleoplasm and cytoplasm

nucleolus

-inside nucleus

-site of ribosomal RNA synthesis

mitosis

normal form of nuclear division in eukaryotic cells; results in two diploid daughter cells

meiosis

specialized form of nuclear division; results in four haploid gametes

mitochondria

THE POWERHOUSE OF THE CELL

-carry out respiration and oxidative phosphorylation for aerobic eukaryotes

-1000+ per cell (few)

-surrounded by two membranes

cristae

folded internal membrane of the mitochondria

matrix

innermost area of mitochondrion; contains acid enzymes

hydrogenosomes

-found in anaerobic, strict fermenters

-similar size to mitochondria

-lack TCA cycle enzymes and cristae

0major function is oxidation of pyyruvate to H2 and CO2, producing CH4--> acetate is secreted

chloroplasts

-chlorophyll-containing organelle found in phototrophic eukaryotes

-have double membrane

stroma

in chloroplasts, this contains large amounts of Rubusico (key for Calvin Cycle)

thylakoids

flattened membrane discs that contain chlorophyll and ATP synthetic components; form proton motive force

endosymbiotic hypothesis

idea that mitochondria nd chloroplasts descended from respiratory and phototrophic bacterial cells, respectively, association with non-phototrophic eukaryal hosts

endoplasmic reticulum (ER)

network of membranes continuous with nuclear membrane

rough ER

-has ribosomes

-major producer of glycoproteins and new membrane material

smooth ER

-lacks ribosomes

-participates in the synthesis of lipids and carbohydrate metabolism

golgi complex

stacks of cisternae that function in concert with the ER (modifies products of ER destined for secretion)

cisternae

membrane-bound sacs in golgi complex

lysosomes

clean up waste in cells and use enzymes to dispose of them

cytoskeleton

internal cell structural support

microtubules

these filaments of cytoskeleton maintain cell shape and motility; move chromosomes and organelles (a & b tubulin)

microfilaments

these filaments of cytoskeleton that maintain cell shape; involved in amoeboid motility and cell division (actin)

intermediate filaments

these filaments of cytoskeleton that maintain cell shape and position of organelles (keratin proteins)

dynein

attached to microtubules and uses ATP to drive motility