Bacteriophages What are Bacteriophages Viruses that attack bacteria

Bacteriophages

What are Bacteriophages Viruses that attack bacteria were observed by Twort and d'Herelle in 1915 and 1917. They observed that broth cultures of certain intestinal bacteria could be dissolved by addition of a bacteria-free filtrate obtained from sewage

Bacteriophages under Electron Microscope

Bacteriophage (Phage) Definition - Obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery Significance Models for animal cell viruses Gene transfer in bacteria Medical applications Identification of bacteria - phage typing Treatment and prophylaxsis? ? ?

Bacteriophages: Definition & History Bacteriophages are viruses that can infect and destroy bacteria. They have been referred to as bacterial parasites, with each phage type depending on a single strain of bacteria to act as host.

BACTRIOPHAGES Like most viruses, bacteriophages typically carry only the genetic information needed for replication of their nucleic acid and synthesis of their protein coats. . They require precursors, energy generation and ribosomes supplied by their bacterial host cell.

Bacteriophages: Classification At present, over 5000 bacteriophages have been studied by electron microscopy and can be divided into 13 virus families.

Bacteriophage Bacteriophages make up a diverse group of viruses, some of which have complex structures, including doublestranded DNA.

Bacteriophage Also known simply as a phage; a virus that attacks and infects bacteria. The infection may or may not lead to the death of the bacterium, depending on the phage and sometimes on conditions. Each bacteriophage is specific to one form of bacteria.

Composition and Structure Composition Nucleic • acid Genome size Modified bases Struc Pr T) P tuoret(ein Contractile Sheath Tail 4 S e Piz rotection H Inefaedctioron – – 11/20/12 Head/Capsid – Tail Fibers Base Plate Dr. T. V. Rao MD's Undergraduate Series 12

Phage entering a bacterial cell

Bacteriophage showing Lytic and lysogenic cycle 12 Dr. T. Rao M grad e Ser 16

Bacteriophages: Virulence Factors Carried On Phage Temperate phage can go through one of two life cycles upon entering a host cell. 1) Lytic: Is when growth results in lysis of the host and release of progeny phage. 2) Lysogenic: Is when growth results in integration of the phage DNA into the host chromosome or stable replication as a plasmid. Most of the gene products of the lysogenic phage remains dormant until it is induced to enter the lytic cycle. 17

Bacteriophages: Lysogenic Conversion Some lysogenic phage carry genes that can enhance the virulence of the bacterial host. For example, some phage carry genes that encode toxins. These genes, once integrated into the bacterial chromosome, can cause the once harmless bacteria to release potent toxins that can cause disease. 18

Bacteriophages • • • Used for cloning foreign genes among other applications Proteins and peptides are fused to the Capsid(surface) of the phage The combination of the phage and peptide is known as a Fusion Protein 19

Bacteriophages • • • Used for cloning foreign genes among other applications Proteins and peptides are fused to the Capsid(surface) of the phage The combination of the phage and peptide is known as a Fusion Protein 20

Bacteriophages • Once these Phages are isolated and recovered they can be used to infect bacteria which will create a particle similar to a monoclonal antibody 21

Lytic and Lysogenic cycle 22

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Bacteriophages: Lysogenic Conversion Examples of Virulence Factors Carried by Phage Gene Product Bacterium Phage Vibrio cholerae CTX phage cholerae toxin cholera Escherichia coli lambda phage shigalike toxin hemorrhagic diarrhea Clostridium botulinum clostridial phages Corynebacterium diphtheriae Streptococcus pyogenes Phenotype botulinum toxin botulism (food poisoning) corynephage beta diphtheria toxin diphtheria T 12 erythrogenic toxins scarlet fever 25

Lysogenic conversion In some interactions between lysogenic phages and bacteria, lysogenic conversion may occur. It is when a temperate phage induces a change in the phenotype of the bacteria infected that is not part of a usual phage cycle. Changes can often involve the external membrane of the cell by making it impervious to other phages or even by increasing the pathogenic capability of the bacteria for a host. 26

Assay for Lytic Phage • Plaque assay Method Plaque forming unit (pfu) – – Bacteria + Phage – Measures infectious particles 27

Lytic vs Lysogenic Cycle 28

Transduction 29

Transduction 30

Bacterial cell wall Bacterial chromosome Capsid Ca S T 1 Attachment: Phage attaches to host cell. 2 Penetration: Phage pnetrates host cell and injects its DNA. Ba Pin Ce P Sh Ta 3 Merozoites released into bloodsteam from liver may infect new red blood cells 11/20/12 Dr. T. V. Rao MD's Undergraduate Series 31

Tail DNA 4 5 Maturation: Viral components are assembled into virions. Capsid Release: Host cell lyses and new virions are released. 11/20/12 Tail fibers Dr. T. V. Rao MD's Undergraduate Series 32

Examples: * Corynebacterium diphtheria produces the toxin of diphtheria only when it is infected by the phage β. In this case, the gene that codes for the toxin is carried by the phage, not the bacteria. * Vibrio cholerae is a non-toxic strain that can become toxic, producing cholera toxin, when it is infected with the phage CTXφ. * Clostridium botulinum causes botulism. * Streptococcus pyogenes causes scarlet fever. * Shiga toxin T's. Unedtreagranduu Dr. T. V. Rao*MD ates Series 11/20/12 33

Medical Applications of Phages “I strongly believe phage could become an effective antibacterial tool” - Carl Merril, Chief of the Laboratory of Biochemical Genetics, National Institute of Mental Health, NIH. “ It might be another string on the bow, such that when (conventional antibiotics) fail, here’s something that has a chance of working. But it’s not going to be a panacea” - Joshua Lederberg, Sackler Foundation Scholar at The Rockefeller University

The Programme Created by Dr. T. V. Rao MD for Undergraduate Learning in Developing Countries Email doctortvrao@gmail. com

Disclaimer: The information provided is based on the latest, most reliable scientific findings. Like all scientific findings, this information is subject to change as more data become available. This short briefing is for informational purposes only and should not be considered medical advice!

FAQ - brief form - more at end! What is the fatality rate? Overall, is estimated at 1 -2%. Varies greatly between populations. About 80% of the cases have been relatively mild. What are the symptoms of COVID-19? Fever, coughing, difficulty breathing. What is the incubation period before symptoms appear? Highly variable – estimated 2 to 14 days Who is at the most risk? The elderly, and those with other conditions such as heart disease, breathing problems, a compromised immune system, etc.

The biology of COVID-19 Electron micrograph of coronaviruses Illustration based on microscopy By Photo Credit: Content Providers(s): CDC/Dr. Fred Murphy This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #4814. By CDC/ Alissa Eckert, MS; Dan Higgins, MAM - This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #23312.

Life-cycle of a coronavirus Discovered in the 1960 s, coronaviruses are known to cause about 30% of all colds (upper respiratory infections) Some coronaviruses, including SARS, MERS, and now COVID-19, are more dangerous than others, primarily because they can also infect the lungs All are RNA viruses that reproduce in human cells by the mechanism shown in the diagram Lanying Du et al (2009) “The spike protein of SARSCo. V - A target for vaccine and therapeutic development. ” Nature Reviews Microbiology 7(3): 226 -36. DOI: 10. 1038/nrmicro 2090

The S (spike) protein on the virus surface allows entry into cells and is the target of vaccine development Structure of the S glycoprotein solved by cryoelectron microscopy. Wrapp et al. 2020. Science.

How contagious is it? Ro is an average number of persons an infected individual will infect. Current estimate of Ro is about 2. 5.

How does COVID-19 spread? - Through droplets produced by an infected person by coughing, sneezing, talking, and through fecal contam. - Droplets may persist on surfaces Droplets travel about 2 meters Each infected person will pass it on to 2 -3 others (on average). for an extended period - Up to 28 days in cold temperatures - Length of persistence depends on environmental conditions, including temperature and humidity - Standard disinfectant measures are effective

Where is the virus now? • Map maintained by Johns Hopkins: https: //gisanddata. maps. arcgis. com/apps/opsdashboard/index. html#/bda 7594740 fd 40299423467 b 48 e 9 ecf 6

What is the fatality rate? Case fatality rate = (number of deaths / number of diagnosed cases)*100 Average CFR = 2. 3%, but CFR is agedependent BUT, number is not calculated with confidence, as number of cases likely larger As of 11 -Feb-2020 http: //weekly. chinacdc. cn/en/article/id/e 53946 e 2 -c 6 c 4 -41 e 9 -9 a 9 b-fea 8 db 1 a 8 f 51

How does COVID-19 compare to other viruses?

How might COVID-19 compare to well-known pandemics? 1918 H 1 N 1 Influenza (“Spanish” flu – though it may have originated at Ft. Riley in Kansas) >0. 5 billion infected (at least 1/3 of the world population at the time) ~10% CFR = 50 -100 million deaths 2009 “swine” flu (atypical H 1 N 1) between 0. 5 and 1. 5 billion people infected ~0. 02% CFR = 250, 000 deaths worldwide (lower even than typical of seasonal flu infection despite being a new pandemic strain, perhaps due to early and aggressive vaccination, isolation, and treatment) typical “seasonal” flu (mostly a mix of H 1 N 1 and H 3 N 2 strains) ~ 1 billion infected worldwide each year (<10 -50 million in US) ~0. 2% CFR = 250, 000 -600, 000 deaths worldwide each year (10, 000 -100, 000 in US) SARS (now SARS-Co. V-1 since COVID-19 is caused by SARS-Co. V-2) ~10, 000 cases in Hong Kong outbreak ~10% CFR = ~1000 deaths (outbreak was contained – debilitating infection not easily spread) References: https: //www. hopkinsmedicine. org/health/conditions-and-diseases/coronavirus-disease-2019 -vs-the-flu https: //www. cdc. gov/flu/pandemic-resources/index. htm https: //hub. jhu. edu/novel-coronavirus-information/

https: //www. cdc. gov/corona virus/2019 ncov/about/preventiontreatment. html

Critical COVID-19 FAQ Q: What is COVID-19? A: New viral infection that is likely to become a global pandemic due to its infectiousness and absence of a current vaccine/treatment Q: What is it caused by? A: The coronavirus SARS-Co. V-2 causes COVID-19. Though it is closely related to the viruses that cause SARS and MERS, it causes infection that more closely resembles influenza (flu). It likely first started as a zoonotic infection (from animals) but is transmitted easily by people. Q: What is the fatality rate? A: Overall, currently estimated at ~2%. Varies greatly between populations. About 80% of the cases have been relatively mild. Q: What are the symptoms of COVID-19? A: Fever, coughing, difficulty breathing, organ failure Q: How are people infected? A: By inhaling respiratory droplets (from coughing and sneezing), by touching a contaminated surface (virus may live up to a month at room temperature). By contact with infected body fluids and feces. Q: What is the incubation period before symptoms appear? A: Highly variable – estimated 2 to 14 days. Completely asymptomatic carriers have been reported. Q: Who is at the most risk? A: The elderly, and those with other conditions such as heart disease, breathing problems, a compromised immune system, etc. Q: What can we do? A: Wash hands before eating and after being in public. Cover mouth and nose when coughing/sneezing. Stay in your home if sick. Follow all government instructions concerning isolation and quarantine if they occur. see https: //www. cdc. gov/nonpharmaceutical-interventions/index. html for general respiratory virus precautions that will help

Community spread via asymptomatic carriers • • • Virus spread from patients with little or no symptoms show are shedding virus. Vast majority of infections are mild allowing community spread Many infections undiagnosed because of mild or no symptoms—thus, percentage of serious cases likely much lower. COVID-19 thought to spread mainly • person to person who are in close contact (~6 feet) • Through respiratory droplets • Possible to get infected by touched a surface, but not the main route. People most contagious when most symptomatic

MORE REFERENCES about fecal transmission: https: //www. tandfonline. com/doi/full/10. 1080/22221751. 2020. 1729071 about asymptomatic transmission: https: //www. sciencealert. com/researchers-confirmedpatients-can-transmit-the-coronavirus-without-showingsymptoms about SARS epidemiology: https: //onlinelibrary. wiley. com/doi/epdf/10. 1046/j. 14401843. 2003. 00518. x about SARS (related coronavirus) persistence on surfaces: https: //www. ncbi. nlm. nih. gov/pmc/articles/PMC 2863430/