micro: chapter 4

How biofilms form

-random collision of cells w/ surface accounts for intial cell attachment -adhesion is promoted by interaction btw one or more cellular structures + surface a. cellular structures promote attachment include protein appendages (pili, flagella) b. cell surface adhesin proteins -attachment of cell to surface is signal for repression of biofilm-specific genes that encode a. synthesis of intracellular + extracellular signaling molecules b. production of extracellular polysaccharides (initiate matrix formation)

Biofilm mechanisms of tolerance:

-slower growth rates in biofilms -reduce penetration of antimicrobial substances through the extracellular matrix -expression of genes that increase tolerance to stress

Biofilms

-typically contain multiple layers of cells embedded in porous matrix material -may contain one or two species, OR several -FUNCTIONAL and GROWING microbial communities, not just cells trapped in sticky matrix -transcriptional profile of cells in biofilm differ from others -formation is initiated by attachment of a cell to a surface followed by expression of biofilm-specific genes -TOLERANT to antibiotics + antimicrobial stressors (1000 times more tolerant than planktonic cells of same species)

Why bacteria form biofilms

1. Self-defense: biofilms better resist -phsyical forces that sweep away unattached cells -phagocytosis by protozoa + host immune system cells -penetration of toxic molecules and anti-microbial compounds 2. Allows cells to remain in favorable niche -biofilms attached to nutrient-rich surfaces (animal tissues) or in flowing systems attach to locations where nutrients are abundant or replenished. 3. Allows bacterial cells to live in close association w/ one another -facilitates cell-to-cell communication and increases chances for survival -cells in close proximity= more opportunities for nutrient + genetic exchange 4. biofilm formation = "default" mode of growth for bacteria in natural environments -nutrient levels significiantly lower in natural environments than lab *Implicated in medical, dental, and industrial settings

Steps in Biofilm formation and dispersal

1. attachement: adhesion of few motile cells to suitable solid surface 2. colonization: intercelluar communication, growth, and polysaccharide formation 3. development: more growth and polysaccharide 4. active dispersal: triggered by environmental factors such as nutrient availability

describe the affect of slime layers & capsules on bacterial virulence. predict what would happen to bacteria.

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Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended

plasma membrane

A selectively-permeable phospholipid bilayer forming the boundary of the cells

capsule

A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces. (prokaryotic)

Define biofilms and specify its properties

Biofilms are multicellular communities of bacteria embedded in a gelatinous matrix called slime. Biofilms adhere to surfaces with electrostatic forces, pili, flagella, and /or a glycocalyx; tolerant of antibiotics and antimicrobials due to chemical gradients within the film; can lead to wound and chronic infections in humans

Define endospores

Defense strategy against hostile conditions; are stable resting stages that barely metabolize & germinate when conditions improve; produced by bacillus & clostridium - dorment stage Sporulation: Endospore formation Germination: Return to vegetative state - An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria from the Firmicute phylum

Examples of biofilms

Dental plaque on teeth Algae n the walls of hte swimming pools Scum that accumulates on shower doors

what is endospores impact on control of microbial growth?

Endospores are considered the most resistant structure of microbes. They are resistant to most agents that would normally kill the vegetative cells from which they formed

list & describe the structures used for movement

Flagella & axial filaments( endoflagella) : provide motility

Histones

Globular protein that assist in DNA packaging in eukaryotes. Histones form octamers around which DNA is wound to form a nucleosome.

What are the names of the two (2) passive processes moving molecules or ions across the plasma membrane? What is the difference between them?

Simple diffusion: overall movement of molecules or ions from area of low concentration to an area of high concentration. Facilitated diffusion: membrane protein functions as channels or carriers that facilitate the movement of ions or large molecules across the plasma membrane. one needs protein the other doesn't

passive transport

The movement of materials through a cell membrane without using energy. from an area of high concentration to low concentration

What is osmosis? Is it a passive or an active process?

The net movement of water molecules across a selectively permeable membrane from an area of high concentration to low (passive transport)

active transport

a cell must expend energy to move a solute against its concentration gradient from an area of low concentration to an area of high concentration.

slime layer

a glycocalyx that is unorganized and loosely attached to the cell wall (prokaryotic)

Define glycocalyx and specify its functions

a sticky layer of polysaccharides secreted externally to the cell wall; it protects cells from the environment and allow them to attach to surfaces; also helps pathogens evade immune system

biofilm impact on human health

contribute to infections of indwelling medical devices and chronic infections. resistant to antibiotic and host immune cells, treatments are costly and ineffective.

list & describe the structures used for attatchment

fimbrae: short, thin fibers built of protein that adhere to each other & surfaces - both are prokaryotic Pilli: longer, hollow fibers built of protein that are used for attatching to toher cels & transferring DNA

Get rid of biofilms

need to physically remove the biofilm or replace w/ colonized material

What is peptidoglycan made of?

polymer of disaccharide - N-acetylglucosamine (NAG) - N-acetylmuramic acid (NAM)

Unusually shaped bacteria

star-shaped and rectangular

aquaporins

water channel proteins

Hypotonic

water moves into the cell. if cell wall is strong, it contains swelling. if cell is weak or damaged, the cell will burst

Hypertonic

water moves out of cell, causing its cytoplasm to shrink

Isotonic

when the concentration of two solutions is the same