Putting Microbes To Work In The Environment Flashcards
Features of biofilms
Ubiquitous
Resistant to antibiotics
Always has to be wet- if it dries out then the bacteria die
Microbial environment- natural
Not created by humans
Complex and changing
Gradient of nutrients and environmental factors (water, pH, temp, O2, pressure, radiation)
Microbes need to be able to switch quickly between different states to adjust to different environments and need to be able to overcome competition
Microbial environment- human body
Associate with each other and other microbes
Forms relationship with host (host has ~39 trillion bacteria mostly in colon, compared to 30 trillion RBCs)
Surviving starvation state is paramount
Morphological changes microbes undergo to survive starvation
Endospores
Nucleoid condensation
Endospores and starvation survivial
Metabolically dormant
Resistant to heat
Dormancy in bacteria
Nucleoid condensation in starvation survival
Ways cells survive without needing to form endospores (as not all bacteria do this)
Nucleoid-association proteins- bind major and minor DNA and bend it= condensation and make different side chains available for genes to survive starvation, these different genes need to be translated
Change in transcription
Stress response pathways
Growth arrest/ slow growth
Starvation proteins in microbes
Transpeptidases- peptidoglycan cross-linking and thickening of cell wall= molecules cant enter or exit
Chaperones- prevent denaturation, help renature damaged proteins
Features of starved microbes (persistent)
Hard to kill and can survive for years
Can become more virulent- giving them nutrients after being starved of them for so long can make them more virulent
Persister cells in starvation survival
Small subset of cells spontaneously dormant and non-growing even with nutrients which prepare for harsh conditions
Develop in mid-exponential phase and will thrive in stress. When given more nutrients, non-persistent cells will take over again and then persisters will form again
Survive antibiotic pressure due to tolerance
Hard to eradicate
Persister cells and biofilms
Bactericidal antibiotic (kills)- persisters survive
Termination of treatment= replenish population
Biofilm environment facilitates persister cells
Difference between antibiotic resistance and tolerance
Resistance= genetic modification
Tolerance= can overcome but not resistant
What are biofilms
Microbial communities that attach to surfaces or themselves
Grow vertically and horizontally
Stages of biofilm development
Reversible attachment- microbes attach if conditions are right but can be detached with force
Irreversible attachment- slowly produce polysaccharide= stick
Maturation- dividing and making more exopolysaccharide
Maturation and dispersion- deeper microbes under more stress so become more tolerant and get modifications to be able to tolerate different conditions, can get antibiotic resistance this way (also close together for HGT)
Biofilm EPS (extracellular polymeric susbtances)
Major component in biofilm= 50-95% weight, chemical composition may be different
Important in maintaining integrity
Preventing dessication
Preventing attack by harmful agents (antibiotics, toxins, host immune cells)
Bind essential nutrients
Advantages of biofilms
Physical attachment on moving environment
Staying in one place
Substrate can be nutrient source
Extracellular enzymes that solubilise food arent rapidly diluted away
Nutrients might be higher in the biofilm than in the environment
Wound biofilms
Delay wound healing
Increase risk of infection- chronic infection, polymicrobial
Protection from body’s natural immune response- inflammatory response may induce biofilm formation
Providing nutrients in form of exudate (dead immune cells)
Damaging healing tissue
Normal wound healing process
Bacteria enter deeper wound
Body produces platelets to heal wound
Mast cells release molecules to recruit macrophages and neutrophils to clear pathogen
Pathogen cleared, above cells release cytokines to induce healing
Wound healing with biofilm present
Arrested in inflammatory phase of wound healing and cannot progress
Prevent blood clot and scab formation so wont close
Body reacts to increased microbes, they feed on host response
How do biofilm bacteria feed on host immune response
Neutrophils and macrophages= proteases which degrade extracellular matrix proteins
Normally, mellatoproteinase levels and activity is controlled
In chronic wounds, expression is derailed so there are more of these enzymes and increased protease activity= enzymes degrade healthy tissue and increase the wound and provide more nutrients for bacteria= promotes colonisation
Bacteria can then secrete further enzymes to degrade tissue for nutrients= impaired wound healing
Biofilms on teeth
Dental plaque
>1000 diff species
Can damage tooth= decay or loss
Receding gums and bad breath from inflammatory response from bacteria entering gum area= more ability to enter
Dental caries, periodontal disease= difficult to remove
Floss and brush regularly
Biofilms on objects and devices
Indwelling catheter most common= UTI, vascular disease
Bacteria can be transferred to external surface of objects or on skin flora of caregivers hand
Piercings, tattoos, brandings
Biofilm prevention
Regular cleanse and debride wound tissue- remove biofilm and prevent maturation
Can be difficult when attached to healthy tissue
Most effective in early stages, more developed biofilm= more unlikely to get rid of it
Biofilm management
Increase frequency of debridement
Cannot completely remove it
Help prevent re-establishment
Without management: re-establishment occurs within 24hr
Can have wound dressings with antibiofilm activity- only good if being regularly changed
Targeted therapy for biofilm infections
Become resistant to most antimicrobials in 48-96hr
Clinical management requires complete removal of infected area/ device
Attack on regular basis= can cause detachment
Making bacteria susceptible for host defenses and treatment
Can cause systemic infections (typically more virulent)
Initial attachment phase of biofilm development
Physical attachment- rough surface or smooth surface (smooth requires laminar flow boundary layer= aerodynamic forces= viscosity and compressibility)
Biological attachment- attach themselves with flagella or fimbriae/ pili
Attachment of mobile bacteria: they become loosely attached in aqueous phase with electrostatic or hydrophobic interactions
Host provides substrate for colonisation of surface (eg teeth or external devices)
Primary colonisation phase of biofilm development
Permanent attachment and symbiotic community, produce EPS and eDNA (viscous)
Interaction with substrate eg hydroxyapatite, plasmic, skin
Interaction mediated by production of EPS
One attached, active growth begins, microcolonies form and further growth to cover surface occurs
Climax community phase of biofilm development
Develops within several days= stable association and integration
Growth continues until steady state- age and diversity and ‘microbial homeostasis’
Diversity= polymicrobial biofilms- can include bacteria that arent able to attach to the substrate or not capable of surviving initial nutritional restrictions
Biofouling (biofilms in industry)
Power plants, air conditioning, food processing, oil refining
Designed to withstand tolerances for optimal efficiency of production- leads to major biofilm issues
Biofilm financial burden
Food industries lose large production runs due to contamination with microbes
Fouling of pipes= friction and plant failure through corrosion
Heat exchanger surfaces= inefficient heat exchange
Cleaning requires closing of plant, physical scrubbing and loss of money due to closing plant
Biofilms in dairy industry
Milk highly perishable
Produced in udder= sterile, once it leaves it is contmainated
High nutrients allows microbes to grow= biofilm is natural state, survive pasteurisation and form biofilms
Biofilms at air-liquid interface as need O2, most commonly from Bascillus
