4. Biofilms Biofilm: a polysaccharide-encased community of microorganisms can grow on many surfaces (catheters, surgical devices, pipes, teeth) extremely resistant to environmental insults (antibiotics, bactericidal agents)
10. Cytoplasmic Membrane & Transport Systems Simple diffusion Movement of permeable molecules along a concentration gradient Facilitated diffusion Movement along a concentration gradient through a protein channel Active transport Movement against a concentration gradient requires energy expenditure Group translocation Chemical alteration of molecule circumvents the concentration gradient
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12. Active Transport ABC Transporters ABC = ATP-binding cassette ATP hydrolysis = energy source 1. Binding protein scavenges nutrient 2. Transporter recognizes binding protein 3. Nutrient pumped into the cell with energy from ATP hydrolysis
13. Transport Systems Group Translocation Chemical alteration of molecule circumvents the concentration gradient Alteration = phosphorylation Phosphorylated nutrient is not equivalent to unphosphorylated nutrient Energy expenditure from phosyphorylation
15. Osmosis and the Cell Wall Simple diffusion Movement along a concentration gradient Osmosis Water flow to eliminate a concentration gradient Osmotic pressure on cytoplasmic membrane results in cell expansion Cell wall allows cell to withstand osmotic pressure
24. Bacteria That Lack a Cell Wall Mycoplasma Sterols strengthen and stabilize cytoplasmic membrane
25. Capsule and Slime Layer Capsule (glycocalyx) Gel-like layer for protection or attachment Distinct and gelatinous Slime layer Gel-like layer for protection or attachment Diffuse and irregular
29. Pili Pili Hollow, helical string of protein subunits arranged as a cylinder Function: 1. attachment (fimbrae) 2. solid media motility (twitching or gliding) 3. conjugation (F pilus or sex pilus)
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31. F Pilus and Conjugation Conjugation DNA transfer from one cell to another Transfer from F+ to F- cell
35. F Plasmid Integration Plasmid Insertion Sequences Allows plasmid integration at homologous sites in the bacterial chromosome Hfr High frequency of recombination
36. Formation of F’ Cell / F’ Plasmid Plasmid can excise from Hfr cell F’ plasmid F plasmid + small piece of chromosomal DNA transferred via conjugation recipients become F+
38. Mechanisms of DNA Transfer Transformation: Cells must be in a specialized (“competent”) state to receive DNA
39. Bacterial Chromosome(s) Nucleoid Irregular, gel-like mass of the chromosome(s) 10% of cell volume Supercoiled DNA allows tight packaging Genomics Utilization of information from large-scale genome sequencing Identification of virulence factors acquisition of virulence factors gene regulatory mechanisms genetic relatedness 2002: 87 bacterial genomes sequenced
40. DNA Transfer Transposable Elements Allows multiple genes to move as a unit from one location (chromosome or plasmid) to another location in the cell
43. Bacterial Ribosomes Ribosomes protein + rRNA components S = Svedberg unit measure of sedimentation mRNA translation & protein synthesis important / conserved process Differences between prokaryotic and eukaryotic ribosomes can be exploited for antimicrobial therapeutics Prokaryotic ribosome (eukaryotic = 80S)
45. Endospores Forms in response to nutrient deprivation Allows cell survival in dormant state Resistant to: heat dessication toxic chemicals UV irradiation Mainly species of Bacillus and Clostridium
46. Endospore Formation Sporulation Occurs when little nitrogen or carbon is present Germination Brief exposure to heat or chemicals Endospore takes on water, swells Spore coat / cortex crack open Vegetative cell grows out 1 endospore = 1 vegetative cell not a means of reproduction
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