Includes definition, classification, history, formation, salient features, gene transfer( conjugation, transformation, transduction), antibiotic resistance, nutritional influence, quorum sensing, role in pathogenesis, and controversies.
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
plant pathogen interaction
different types of pathogens
gene for gene hypothesis
direct receptor model
Elicitor receptor model
suppersor repressor model
gaurd hypothesis
Management of host plant resistance through immunizationAnshul Arya
it is a small presentation prepared for seminar purpose .immunization is a new technique very few people know about it even i did not get any slide prepared by it earlier even whatever i got was not purchased .so i prepared it for those who are interested to know about it without having problems to find the matter for it.
Hi there,
This was topic on which I presented a talk in our department. As we know Insecticide such as pyrethroids are being most widely used for controlling insect pest in agriculture because of their safe, cheap, effective and long-lasting nature (Bulter et al. 2011). However, the widespread development of insecticide resistance, especially resistance to pyrethroid and the fact that resistance to an insecticide generally confers cross-resistance to other insecticides has become a serious problem challenging the control of agriculturally, economically, and medically important insect pests and resulting in increase of insect vector-borne diseases in many parts of the world (Zaim 2002; Bulter 2011). Three major mechanisms are involved in insecticide resistance: (1) increased metabolic detoxification of insecticides; (2) decreased sensitivity of the target proteins on which an insecticide acts, known as target site insensitivity; and (3) decreased cuticular penetration/or increased sequestration/storage.
Bacillus thuringiensis(Bt)Cry protein is one of the most effective biopesticides that can act against a large group of insect orders like Lepidoptera, Coleoptera, Diptera etc. But through the course of evolution insects have developed resistance so that they can combat against Bt. Mutation(s) in the target site; reduced protease activity; sequestration of toxin molecules; mutations in the ABCC2 transporter protein are few mechanisms which govern resistance in insects against Cry protein. Therefore, it has become prime importance to understand the molecular basis of insect resistance and what could be the strategies by which the efficacy of the Cry protein can be enhanced. The strategies for improving the efficacy of Cry toxin are (i) Expression of chitinase gene along with Cry toxins; (ii) Expression of hybrid toxin; (iii) Introduction of intramolecular cleavage sites. The insects have developed resistance against different groups of Cry proteins such as Cry2Aa, Cry1Ac, Cry2Ab etc. But the relative fitness (such as larval and pupal weight, pupal duration, and survival rate, etc.) in resistant larvae is much lower than the susceptible larvae because of genetic changes in insects. One of such genes that affects the relative fitness in Helicoverpa armigera is death associated LIM only protein (Ha-DALP) which is basically involved in cell signalling, cell fate determination, transcriptional regulation of gene expression etc.
"Bio - Warfare During Host Pathogen Interactions in Indigenous Crop Plants" b...Md. Kamaruzzaman
This is a analysis of some collected information of the subject of my M.S. theory semester. Course title was Plant Pathogenesis and Genetics of Plant Pathogens
Microorganisms cause virtually all pathoses of the pulp and periapical tissues.
Once bacterial invasion of pulp tissues has taken place, both non-specific inflammation and specific immunologic response of the host have a profound effect on the progress of the disease.
Endodontic infection develops in root canals devoid of host defenses,
pulp necrosis (as a sequel to caries, trauma, periodontal disease,or iatrogenic operative procedures)
or pulp removal for treatment.
Biofilm-induced oral diseases.
ROUTES OF ROOT CANAL INFECTION
Caries
• Trauma-induced fractures
• Cracks
• Restorative procedures
• Scaling and root planing
• Attrition
• Abrasion
• Gaps in the cementoenamel junction
at the cervical root surface
• Dentinal tubules
• Direct pulp exposure
• Periodontal disease
• Anachoresis
Mechanisms of Microbial Pathogenicity and Virulence Factors
Pathogenicity : The ability of a microorganism to cause disease.
Virulence: Degree of pathogenicity of a microorganism.
Some microorganisms routinely cause disease in a given host and are called primary pathogens.
Other microorganisms cause disease only when host defenses are impaired and are called opportunistic pathogens by changing the balance of the host–bacteria relationship.
Bacterial strategies that contribute to pathogenicity include the ability to coaggregate and form biofilms.
In the pathogenesis of primary apical periodontitis
Bacteria in caries lesions form authentic biofilms adhered to dentin.
Diffusion of bacterial products through dentinal tubules induces pulpal inflammation
After pulp exposure, the exposed pulp tissue is in direct contact with bacteria and their products
and responds with severe inflammation. Some tissue invasion by bacteria may also occur.
Bacteria in the battlefront have to survive the attack from the host defenses and at the same time acquire nutrients to keep themselves alive.
In this bacteria–pulp clash, the latter invariably is “defeated” and becomes necrotic, so bacteria move forward and “occupy the territory”—that is, they colonize the necrotic tissue.
These events advance through tissue compartments, coalesce, and move toward the apical part of the canal until virtually the entire root canal is necrotic and infected.
At this stage, involved bacteria can be regarded as the early root canal colonizers or pioneer species (play an important role in the initiation of the apical periodontitis disease process, modify the environment, making it conducive to the establishment of other bacterial groups)
Management of host plant resistance through immunizationAnshul Arya
it is a small presentation prepared for seminar purpose .immunization is a new technique very few people know about it even i did not get any slide prepared by it earlier even whatever i got was not purchased .so i prepared it for those who are interested to know about it without having problems to find the matter for it.
Hi there,
This was topic on which I presented a talk in our department. As we know Insecticide such as pyrethroids are being most widely used for controlling insect pest in agriculture because of their safe, cheap, effective and long-lasting nature (Bulter et al. 2011). However, the widespread development of insecticide resistance, especially resistance to pyrethroid and the fact that resistance to an insecticide generally confers cross-resistance to other insecticides has become a serious problem challenging the control of agriculturally, economically, and medically important insect pests and resulting in increase of insect vector-borne diseases in many parts of the world (Zaim 2002; Bulter 2011). Three major mechanisms are involved in insecticide resistance: (1) increased metabolic detoxification of insecticides; (2) decreased sensitivity of the target proteins on which an insecticide acts, known as target site insensitivity; and (3) decreased cuticular penetration/or increased sequestration/storage.
Bacillus thuringiensis(Bt)Cry protein is one of the most effective biopesticides that can act against a large group of insect orders like Lepidoptera, Coleoptera, Diptera etc. But through the course of evolution insects have developed resistance so that they can combat against Bt. Mutation(s) in the target site; reduced protease activity; sequestration of toxin molecules; mutations in the ABCC2 transporter protein are few mechanisms which govern resistance in insects against Cry protein. Therefore, it has become prime importance to understand the molecular basis of insect resistance and what could be the strategies by which the efficacy of the Cry protein can be enhanced. The strategies for improving the efficacy of Cry toxin are (i) Expression of chitinase gene along with Cry toxins; (ii) Expression of hybrid toxin; (iii) Introduction of intramolecular cleavage sites. The insects have developed resistance against different groups of Cry proteins such as Cry2Aa, Cry1Ac, Cry2Ab etc. But the relative fitness (such as larval and pupal weight, pupal duration, and survival rate, etc.) in resistant larvae is much lower than the susceptible larvae because of genetic changes in insects. One of such genes that affects the relative fitness in Helicoverpa armigera is death associated LIM only protein (Ha-DALP) which is basically involved in cell signalling, cell fate determination, transcriptional regulation of gene expression etc.
"Bio - Warfare During Host Pathogen Interactions in Indigenous Crop Plants" b...Md. Kamaruzzaman
This is a analysis of some collected information of the subject of my M.S. theory semester. Course title was Plant Pathogenesis and Genetics of Plant Pathogens
Microorganisms cause virtually all pathoses of the pulp and periapical tissues.
Once bacterial invasion of pulp tissues has taken place, both non-specific inflammation and specific immunologic response of the host have a profound effect on the progress of the disease.
Endodontic infection develops in root canals devoid of host defenses,
pulp necrosis (as a sequel to caries, trauma, periodontal disease,or iatrogenic operative procedures)
or pulp removal for treatment.
Biofilm-induced oral diseases.
ROUTES OF ROOT CANAL INFECTION
Caries
• Trauma-induced fractures
• Cracks
• Restorative procedures
• Scaling and root planing
• Attrition
• Abrasion
• Gaps in the cementoenamel junction
at the cervical root surface
• Dentinal tubules
• Direct pulp exposure
• Periodontal disease
• Anachoresis
Mechanisms of Microbial Pathogenicity and Virulence Factors
Pathogenicity : The ability of a microorganism to cause disease.
Virulence: Degree of pathogenicity of a microorganism.
Some microorganisms routinely cause disease in a given host and are called primary pathogens.
Other microorganisms cause disease only when host defenses are impaired and are called opportunistic pathogens by changing the balance of the host–bacteria relationship.
Bacterial strategies that contribute to pathogenicity include the ability to coaggregate and form biofilms.
In the pathogenesis of primary apical periodontitis
Bacteria in caries lesions form authentic biofilms adhered to dentin.
Diffusion of bacterial products through dentinal tubules induces pulpal inflammation
After pulp exposure, the exposed pulp tissue is in direct contact with bacteria and their products
and responds with severe inflammation. Some tissue invasion by bacteria may also occur.
Bacteria in the battlefront have to survive the attack from the host defenses and at the same time acquire nutrients to keep themselves alive.
In this bacteria–pulp clash, the latter invariably is “defeated” and becomes necrotic, so bacteria move forward and “occupy the territory”—that is, they colonize the necrotic tissue.
These events advance through tissue compartments, coalesce, and move toward the apical part of the canal until virtually the entire root canal is necrotic and infected.
At this stage, involved bacteria can be regarded as the early root canal colonizers or pioneer species (play an important role in the initiation of the apical periodontitis disease process, modify the environment, making it conducive to the establishment of other bacterial groups)
Microbiology of Endodontic Infection.Mechanisms of Microbial Pathogenicity and Virulence Factors
Biofilm and Community-Based Microbial Pathogenesis
Biofilm and Bacterial Interactions
Biofilm Community Lifestyle
Quorum Sensing—Bacterial Intercommunication
Methods for Microbial Identification
Diversity of the Endodontic Microbiota
Primary Intraradicular Infection
Spatial Distribution of the Microbiota
Microbial Ecology and the Root Canal Ecosystem
Secondary/Persistent Infections and Treatment Failure
Journal club: Lidocaine and Sodium hypochlorite interactionMrinaliniDr
In vitro assessment of the interaction between lidocaine hydrochloride and sodium hypochlorite on root canal dentin before and after chemomechanical instrumentation procedures
David H Pashley: Clinical considerations of microleakageMrinaliniDr
Microleakage and its effect. Includes factors affecting microleakage, the role of smear layer, cytotoxicity of dental materials, blood flow, lymphatics in pulp
Internal anatomy of pulp space. Includes history, development of pulp, classification of the root canal, isthmus, root canal ramifications, regressive changes, apical root anatomy, variations in pulpal anatomy, methods of determining anatomy, pulp space anatomy of permanent teeth.
Techniques of direct composite restorationMrinaliniDr
Techniques of the direct composite restoration. Includes different instruments, matrix system, wedges, bevel, etching, bonding, and placement of composite along with finishing and polishing and clinical management
Management of biofilm in endodontics. History, Classification, use of sodium hypochlorite, EDTA, Chlorhexidine, recent irrigants, LASERS, Ultrasonics, Natural agents, Nanoparticles and probiotics
Hand instruments in operative dentistryMrinaliniDr
Hand instruments in operative dentistry. Includes definition, history, classification, instrument design, instrument formula, parts, nomenclature, grasps, rests and guards, sharpening of instruments and recent advances
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
3. A biofilm is defined as “an assemblage of microbial
cells that is irreversibly associated with a surface and
enclosed in a matrix of primarily polysaccharide
material
-Kelley, 2017
4. Earliest evidence of
organisms in the fossil:
form of stromatolites,
thought to be fossilized
remnants of
cyanobacterial biofilms
The oldest of these
fossils are dated at 3.4
billion years old
5. Anthony van Leeuwenhoek
(1632–1723) : aggregated
small animalcules in the
‘scurf of the teeth’
Louis Pasteur (1822–1895):
aggregates of bacteria as the
cause of wine becoming
acetic
6. Bill Costerton introduced
‘biofilm’ growth in medical
microbiology in 1985
Demonstrated increased
resistance of biofilm-
growing compared with
planktonically growing
bacteria
10. More resilient to stress
Persisters: Do not divide:
Resistant to many
antibiotics
Antibiotics: Cannot penetrate
EPS, Get neutralised,Bacteria
goes in physiologically
dormant state
Crossfeed: Close
proximity
11. Epstein:
Members of the community periodically wakes up
Send out scouts to test the environment
If adverse environment is not
present
Send signal to the remaining cells to resume
14. Van Der Wall
forces and
Secretory adhesive
molecule
Role of
environment
Role of gene
Initially: Conditioning film (Loeb & Neihof) composed of
polymers of the medium
15. Upregulation of gene
Moist environment Rough surface Less shear stress
Characteristics of cell: Flagella, Pili, Fimbriae, Glycocalyx
Expression of 800 genes have been
shown to be altered when single
bacterium species joins a biofilm
17. Further layer of microbes and Extrapolysachharide: Complex
3D-structure
WATER CHANNELS: Transport of nutrients, and oxygen to the cells
18. SEEDING DISPERSAL/SWARMING:
Either a clump of cells or individual cells burst out to seek a
new home.
Inner region liquifies so that the outer stationary bacteria swim
out leaving a hollow mound.
19.
20. Programmed detachment :
Niduses of acute infection
As the bacteria in a biofilm are
protected by matrix host, host
immune system less likely mount a
response
Planktonic bacteria periodically
released: Each time immune
system becomes aware and
inflammatory response leading to
disease symptom:
CAUSE OF CHRONIC
RELAPSE IN INFECTION
21. If chronic bacteria form simply
kills its host, no longer have a
place to live
Infectious agent never kill the host,
neither host is ever able to fully get
rid of pathogens
22. Nutrition influence
Nutrient stress:
alterations in their cell
morphology and cell
surfaces, which
enhance adherence.
Oral cavity:
environment is less
extreme, and saliva
provides a constant
source of nutrients.
Catabolic cooperation
among oral bacteria
allows carbon and
nitrogen from salivary
glycoproteins to be
utilized.
23. The initial
conditioning film
Adherence of
pioneer bacteria
Production of
matrix
Bacterial
competition in the
later stages of
accumulation
The type and
availability
of nutrient
24.
25. Process of cell–cell communication
that allows bacteria to share
information about cell density and
adjust gene expression accordingly
Enables bacteria to express
energetically expensive processes as
a collective only when the impact of
those processes on the environment
or on a host will be maximized
26. These processes include(Novick and Gissinger, 2008)
symbiosis, virulence, competence, conjugation, antibiotic
production, motility, sporulation, and biofilm formation
Gram-negative bacteria : acylated homoserine lactones as
autoinducers
Gram-positive bacteria: processed oligo-peptides
27. 3 BASIC
PRINCIPLES
1. At low cell density : AIs diffuse away, and, therefore, are
present at concentrations below the threshold required for
detection.
At high cell density : the cumulative production of AIs leads to a
local high concentration, enabling detection and response (Kaplan
and Greenberg 1985)
2. AIs are detected by receptors that exist in the cytoplasm or in
the membrane
3. In addition to activating expression of genes , detection of AIs
results in activation of AI production (Novick et al. 1995)
37. Presence of gene-
encoding resistance to β-
lactam, tetracycline, and
glycopeptide antibiotics
in metagenome samples
of 30,000-year-old
permafrost.
Gut microbiome of a pre-
Columbian Andean
mummy from Peru (14C
dating of 980–1170 AD):
harbor genes with
homology to βlactam,
fosfomycin,
chloremphenicol,
Aminoglycosides,
macrolide, quinolones,
tetracycline and
vancomycin resistant
genes.
1st bacterial isolate
deposited in the UK
National Collection of
Type Cultures : strain of
Shigella flexneri that
killed a young soldier in
World War I.
Isolated in 1915, carry
resistance genes for
penicillin and
erythromycin when it
was revived and
sequenced in 2014
D’Costa et al,
2011
Santiago-
Rodriguez et al,
2015
Mather et al.,
2014
38. Most antibiotics in medical use: derived from or produced by a
group of soil-dwelling bacteria called the Actinomycetes.
Most notable genus for antibiotic production : Streptomyces
Producers of specialized metabolites (“natural products”):
antibiotics streptomycin, tetracycline, chloramphenicol,
erythromycin, and vancomycin.
These organisms must be resistant to the antibiotics they
produce, or they would succumb to their own toxic metabolites.
Original sources for many of the antibiotic-resistance genes
circulating in the clinic today
39. •Antibiotic resistance in M. tuberculosis : exclusively by
spontaneous mutation.
•Staphylococcus aureus: Nasal commensal in 30% population.
1959: Introduction to methicillin, after 3 years Methicillin
resistant Staph aureus were reported.
Recently it became CA-MRSA(Community acquired)
•Most common distribution : beta lactamase gene
40.
41.
42.
43. ROLE OF BIOFILM IN PATHOGENESIS
Staphylococcus
epidermidis: impede
the colonisation of
potentially pathogenic
bacteria through the
stimulation of host-
cell immune defences
and the prevention of
adhesion
Cystic fibrosis:
P. aeruginosa undergoe
s a transition from an
acute virulent pathogen
to a CF-adapted
pathogen, allowing it
to persist in the lung
for years or even
decades
44. Overproduction of the matrix polysaccharide alginate
Formation of a mucoid biofilm
Tolerates antibiotics, components of both the innate and adaptive
immune response, and resists phagocytosis
Persistence of these mucoid biofilms within the CF lung
Development of a distinct antibody response
Chronic inflammation mediated by granulocytes, and results in severe
damage to the lung tissue of CF patients
47. Extreme resistance to antibiotics and many other
conventional antimicrobial agents.
Extreme capacity for evading the host defences.
48. Tolerance and Resistance
All bacteria can become resistant, irrespective of their growth
phenotypes, whereas only bacterial aggregates adapt by
exhibiting biofilm tolerance.
Caused by following factors:
3D architecture: presence of several layers of bacteria
promotes the development of nutrient and oxygen gradients and
slows down growth in the core of the aggregate
Matrix components can bind and/or neutralize antimicrobial
agents
Presence of areas within a biofilm that are inhabited by
stationary phase or even dormant bacteria
49. Frustrated phagocytosis: phagocytes do come in contact
with the bacteria in biofilms and they can even penetrate
biofilms. However, the bacteria in the biofilms are not killed.
Defence mechanism: chemical, as bacteria in biofilms can
produce compounds that disable or even kill PMNs
Quorom sensing
50.
51. 1. Cieplik F, Jakubovics NS, Buchalla W, Maisch T, Hellwig E,
Al-Ahmad A. Resistance Toward Chlorhexidine in Oral Bacteria–
Is There Cause for Concern?. Frontiers in microbiology. 2019;10.
2. Bjarnsholt T. The role of bacterial biofilms in chronic infections.
Apmis. 2013 May;121:1-58.
3. Davies J, Davies D. Origins and evolution of antibiotic
resistance. Microbiol. Mol. Biol. Rev.. 2010 Sep 1;74(3):417-33.
4. Donlan RM. Biofilms: microbial life on surfaces. Emerging
infectious diseases. 2002 Sep;8(9):881.
5. Crouzet M, Le Senechal C, Brözel VS, Costaglioli P, Barthe C,
Bonneu M, Garbay B, Vilain S. Exploring early steps in biofilm
formation: set-up of an experimental system for molecular studies.
BMC microbiology. 2014 Dec 1;14(1):253.
REFERENCES
52. 6. Kampf G. Acquired resistance to chlorhexidine–is it time to
establish an ‘antiseptic stewardship’initiative?. Journal of
Hospital Infection. 2016 Nov 1;94(3):213-27.
7. Bowden GH, Li YH. Nutritional influences on biofilm
development. Advances in dental research. 1997 Apr;11(1):81-99.
8. Shintani M, Sanchez ZK, Kimbara K. Genomics of microbial
plasmids: classification and identification based on replication
and transfer systems and host taxonomy. Frontiers in
microbiology. 2015 Mar 31;6:242.
9. Miller MB, Bassler BL. Quorum sensing in bacteria. Annual
Reviews in Microbiology. 2001 Oct;55(1):165-99.
10. Rutherford ST, Bassler BL. Bacterial quorum sensing: its role
in virulence and possibilities for its control. Cold Spring Harbor
perspectives in medicine. 2012 Nov 1;2(11):a012427.
53. 11. Chandki R, Banthia P, Banthia R. Biofilms: A microbial home.
Journal of Indian Society of Periodontology. 2011 Apr;15(2):111.
12. Okuda KI, Nagahori R, Yamada S, Sugimoto S, Sato C, Sato
M, Iwase T, Hashimoto K, Mizunoe Y. The composition and
structure of biofilms developed by Propionibacterium acnes
isolated from cardiac pacemaker devices. Frontiers in
microbiology. 2018 Feb 14;9:182.
13. Muhsin J, Ufaq T, Tahr H, Saadia A. Bacterial Biofilm: Its
composition, Formation and role in human infections. Journal of
Microbiology and Biotechnology. 2015;4:1-4.
14. Høiby N. A personal history of research on microbial biofilms
and biofilm infections. Pathogens and disease. 2014 Apr
1;70(3):205-11.
Editor's Notes
Stromatolite, layered deposit, mainly of limestone, formed by the growth of blue-green algae (primitive one-celled organisms)
For two billion years after they first appeared on Earth, these photosynthetic biofilms produced biomass in prodigious amounts with oxygen as a by-product. During that early period the oxygen was almost instantly tied up in chemical reactions with the components of a highly reducing atmosphere and landscape. But eventually oxygen production outstripped oxygen consumption and for the first time, at about 2.8 billion (check this date) years ago, free oxygen began to appear in the atmosphere. It was at this point that the first curious banded iron deposits, and later the extensive red bed iron deposits, were formed
Protista: Algae, amoeba, slime moulds
Caldwell et al.[14] highlighted four characteristics of
biofilm as follows:
• Autopoiesis – Must possess the ability to
self‑organize
• Homeostasis – Should resist environmental
perturbations
• Synergy – Must be more effective in association
than in isolation
Communality – Should respond to environmental
changes as a unit rather than as single individuals
Besides passive dispersal, brought about by shear stresses, A way to perceive environmental changes and gauge whether it is still beneficial to reside within the biofilm or whether it is time to resume a planktonic lifestyle. Biofilm dispersal can be the result of several cues, such as alterations in nutrient availability, oxygen fluctuations and increase of toxic products, or other stress-inducing conditions
The phosphorylated response regulator activates transcription of the genes in the QS regulon (Fig. 1A). In some cases of Gram-positive bacterial QS, AIPs are transported back into the cell cytoplasm where they interact with transcription factors to modulate the transcription factor’s activity and, in turn, modulate gene expression changes (Fig. 1B)
In his Nobel lecture, Fleming spoke of a hypothetical situation where a person self-treats a sore throat with antibiotics, “He buys some penicillin and gives himself, not enough to kill the streptococci but enough to educate them to resist penicillin.” He advised, “If you use penicillin, use enough.
Tolerance means that bacteria are not killed, although they are unable to grow in the presence of the drug, whereas resistance allows bacteria to grow in the presence of antibiotics
