Biology Club Bulletin #2
The Deadly Killers: Virus & Bacteria
Inside: H. Pylori Bacteria
Virus vs Bacteria
Ebola Virus
Zika Virus
Jokes, Puzzles and more!!
Table of Contents 1) OUR ACTIVITIES! .................................................................................................................... 3 2) WHAT ARE BACTERIA AND VIRUSES? ...................................................................................4 3) BACTERIA VS VIRUS ............................................................................................................... 5 4) BACTERIA...............................................................................................................................6 4.1 Basic Information .............................................................................................................6 4.2 Mechanism- Reproduction .................................................................................................8 4.3 Mechanism- Pathogenicity .............................................................................................. 11 5) VIRUSES ............................................................................................................................... 15 5.1 Basic Information ............................................................................................................ 15 5.2 Mechanism......................................................................... Error! Bookmark not defined. 5.3 Examples of Viruses......................................................................................................... 17 5.3.1 Zika Virus .................................................................................................................. 17 5.3.2 Ebola Virus................................................................................................................ 20 6) Puzzle game!........................................................................................................................ 23 7) References ........................................................................................................................... 24
**Remember to join Biology Club’s activities in the following months -bring your membership card with you as well! :)**
1) OUR ACTIVITIES! Thank you for joining our previous activities: DNA extraction, Cheese making and Mouse Dissection workshops! :D Hope that you had a great time in learning Biology!
Future activities:
Early April: Bio Econ LSS Triathlon April 15th: Leaf Bookmark making workshop (Book Week) April 25th-29th: Science Week May: Talk by HKU professor (with Chem club)
We look forward to seeing you in our activities! :D
2) WHAT ARE BACTERIA AND VIRUSES? You know that bacteria and viruses are everywhere around us. You know that they are the causes of many different diseases. But what exactly are they?
3) BACTERIA VS VIRUS
4) BACTERIA 4.1 Basic Information Bacteria are prokaryotic microorganisms belonging to the two domains: Domain Bacteria and Domain Archaea, in the three-domain-six-kingdom classification system. They are usually a few micrometers (µm) long. 1 gram of soil: 40 million bacterial cells 1 mL of water: 1 million bacterial cells Bacterial cells appear in three main shapes: Bacilli, Cocci and Spirilla.
Bacilli (rod-shaped bacterial cells) Examples include: Pseudomonas aeruginosa (causes pneumonia)
Bacillus thuringiensis (used as biological pesticide)
Cocci (spherical bacterial cells) Examples include: Staphylococcus hominis (causes infection in patients with weak immune system) Escherichia coli (decompose undigested food in intestines of animals, may cause food poisoning in some cases)
Spirilla (spiral bacterial cells) Examples include: Leptospira interrogans (causes leptospirosis)
4.2 Mechanism- Reproduction Bacteria can reproduce by asexual and sexual methods. Most bacteria reproduce by binary fission, and only some of them undergo binary fission + fragmentation. 4.2.1 Asexual reproduction (1) Binary fission Commonest type Favorable conditions: cell divides into two similar daughter cells. The daughter cells soon grow to maturity within 20-30 minutes (2) Budding Used by some bacteria Bud develops at one end of the cell Genome replication -> one copy of the genome gets into the bud Bud enlarges-> become a daughter cell ->gets separated from the parent cell (3) Fragmentation Used by some bacteria Filaments / colony of bacteria break down into small pieces -> each piece develops into a new colony of bacteria Not the major mode of reproduction
(4) Endospore formation
Used by some (Gram-positive bacteria) bacteria as a survival strategy to overcome unfavorable conditions Secretion of a hard resistant wall in response to nutrient deprivation Very resistant to extreme physical conditions and chemicals (eg. high temperature, high UV irradiation, desiccation) During favorable conditions: spore wall ruptured, protoplasmic mass gives rise to a new bacterium
Endospore Formation 4.2.2 Sexual reproduction Sexual reproduction occurs in the form of genetic recombination. (1) Transformation Genetic material of one bacterial cell goes into another bacterial cell Converts one type of bacterium into another type (non- capsulated -> capsulated form) (2) Transduction Genetic material of one bacterial cell goes to other bacterial cell by agency of bacteriophages/ phages (viruses, infecting bacteria) (3) Conjugation Cell to cell union occurs between two bacterial cells DNA of one bacterial cell goes to another cell lengthwise through conjugation tube which is formed by sex pili.
4.3 Mechanism- Pathogenicity
Pathogen: a microorganism that is able to cause disease in a plant, animal or insect Pathogenicity: the ability to produce disease in a host organism, while the degree of pathogenicity is expressed in terms of virulence Determinants of virulence of a pathogen are any of its genetic, biochemical or structural features that enable it to produce disease in a host. Bacterial pathogenicity includes 2 major mechanisms:
4.3.1 Invasiveness - The ability to invade a tissue
Invasion is aided by the production of bacterial extracellular substances, invasins, which act against the host by breaking down primary or secondary defenses of the body. Most invasins are proteins (enzymes) that act locally to damage host cells and/or have the immediate effect of facilitating the growth and spread of the pathogen.
4.3.2 Toxigenesis - The ability to produce toxins Bacteria may produce two types of toxins called exotoxins and endotoxins.
Exotoxins are released from bacterial cells
Endotoxins are cell-associated substance
Most of the toxins are thought of as exotoxins, since they are "released" from the bacteria and act on host cells at a distance.
Both types of bacterial toxins may be transported by blood and lymph -> cause cytotoxic effects at tissue sites other than the original point of invasion or growth.
The toxins are soluble proteins secreted by living bacteria during growth.
Production generally specific to a particular bacterial species (e.g. only Clostridium tetani produces tetanus toxin)
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Protein toxins resemble enzymes: both are proteins; are denatured by heat, acid, proteolytic enzymes; have a high biological activity; and exhibit specificity of action
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Bacterial protein toxins are highly specific in the substrate in their mode of action. Examples of substrates (in the host): tissue cells, organs, or body fluid
4.4 Examples of Bacteria Helicobacter pylori
What is Helicobacter pylori?
Gram-negative bacterium (cannot retain crystal violet stain using the Gram-staining method, for more information, see here)
Microaerophilic bacterium (needs oxygen to survive) that is usually found in the stomach
Spiral-shaped bacteria that grow in the digestive tract and have a tendency to attack the stomach lining.
Infections are usually harmless, but they are responsible for the majority of ulcers in the stomach and small intestine
Adapted to live in the harsh, acidic environment of the stomach. These bacteria can change the environment around them and reduce its acidity so they can survive.
The shape of Helicobacter pylori: penetrate the stomach lining, where the mucus provides protection Body’s immune cells are unable to reach them. The bacteria can interfere with the immune response and ensure that they’re not destroyed.
Causes of Helicobacter pylori The cause of the spread of Helicobacter pylori is not clear. This type of bacteria has co-existed with humans for thousands of years. It may be spread through contaminated water or food. The bacteria is thought to cause stomach problems they penetrate the stomach’s mucus lining and causes low grade inflammation. Symptoms of Helicobacter pylori infection
The infection of Helicobacter pylori is usually asymptomatic Symptoms: upper abdominal pain, loss of appetite, nausea, vomiting, and bleeding into the gastrointestinal tract
Treatment for Helicobacter pylori infection Triple therapies are administered for 10-14 days. The treatment regimens are omeprazole, amoxicillin, and clarithromycin (OAC) for 10 days; bismuth subsalicylate, metronidazole, and tetracycline (BMT) for 14 days; and lansoprazole, amoxicillin, and clarithromycin (LAC), which has been approved for either 10 days or 14 days of treatment. These regiments have reported cure rates of 85-90%.
5) VIRUSES 5.1 Basic Information Viruses are often mixed up with bacteria. In fact they are very different. Viruses are not living organisms, they are non-cellular entities, as they only show one out of seven characteristics of life: reproduction. They also do not have a full cell structure. Instead of a cell membrane or a cell wall, they have a protein coat/ capsid which protects the DNA or RNA material inside. Some have a lipid membrane covering the protein coat. Viruses kills cells in the process of virus reproduction, while having a fast reproduction rate, viruses can kill a lot of animal cells -- enough to cause a disease.
5.2 Mechanism The mechanism of a virus is not as complex as bacterial cells, as its actions� is mainly for one purpose: reproduction. There are a few basic steps that all infecting viruses follow and these are called the lytic cycle. These include: 1. Adsorption: a virus particle attaches to a host cell 2. Entry: The particle injects its DNA or RNA into the host cell 3. The invading DNA or RNA takes over the cell and recruits the host’s enzymes 4. Replication: the cellular enzymes start making new virus particles 5. Assembly: The particles of the virus created by the cell come together to form new viruses 6. Release: the newly formed viruses kill the cell so that they may break free and search for a new host cell The host cell of a virus can be from an animal, plant, fungi, protozoa, or bacteria. Here is a diagram showing the reproductive mechanism:
5.3 Examples of Viruses 5.3.1 Zika Virus As of early 2016, a widespread outbreak of Zika fever, caused by the Zika virus, is ongoing, primarily in the Americas. The outbreak began in April 2015 in Brazil, and has spread to other countries in South America, Central America, Mexico, and the Caribbean. So‌ what exactly is the Zika virus? What is Zika virus? Zika virus is the virus responsible for Zika virus infection -- a mosquitoborne disease. Zika virus is enveloped and icosahedral and has a non- segmented, singlestranded, positive-sense RNA genome. Transmission: by daytime-active mosquitoes (Aedes mosquitoes) as its main vector, sexually transmitted or transmitted through blood. The Zika virus belongs to Flaviviridae, which means humans and other mammals serve as their natural hosts. Diagram about the external and internal structure and features of Zika virus:
Symptoms of Zika virus infection Most Zika virus infection is asymptomatic The most common symptoms: fever and skin rash, conjunctivitis, muscle or joint pain and general malaise Other complications concerned: Adverse pregnancy outcome such as microcephaly (it is not proved to be associated with Zika virus infection yet) Neurological and autoimmune complications, eg. Guillain-Barré Syndrome
Vaccine development for Zika virus An Indian company, Bharat Biotech International, reported in early February 2016 that it was working on vaccines for the Zika virus. The company is working on two approaches to a vaccine:  "recombinant": involving genetic engineering  "inactivated": where the virus is incapable of reproducing itself but can still trigger an immune response Ways to prevent mosquito proliferation 1. - Prevent accumulation of stagnant water - Change the water in vases once a week - Clear the water in the saucers under potted plants every week - Cover water containers tightly - Ensure air-conditioner drip trays are free of stagnant water - Put all used cans and bottles into covered dustbins 2. Pregnant women should postpone any travel to places where the Zika virus is currently of concern (according to CDC)
5.3.2 Ebola Virus We all know this name, Ebola. In 2014, West Africa saw its largest outbreak of Ebola Virus in history, which spread from Guinea to Sierra Leone and Liberia, by air (1 traveler) to Nigeria and USA (1 traveler), and by land to Senegal (1 traveler) and Mali (2 travelers). What is the Ebola Virus? The Ebola virus causes an acute, serious illness which is often fatal if untreated. Ebola virus disease (EVD) first appeared in 1976 in 2 simultaneous outbreaks, one in what is now, Nzara, South Sudan, and the other in Yambuku, Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name. Ebola carries a negative-sense RNA genome in virions that are cylindrical/tubular, and contain viral envelope, matrix, and nucleocapsid components. Ebola virus is one of five known viruses within the genus Ebolavirus. Four of the five known ebolaviruses cause severe and often fatal hemorrhagic fever in humans and other mammals, known as Ebola virus disease (EVD). Here is a diagram showing the structure of Ebola virus:
What is Ebola virus disease? Ebola virus disease, formerly known as the Ebola hemorrhagic fever, is an often fatal disease in humans. The average fatality rate of the Ebola virus disease is 50%, which varied from 25% to 90% in previous outbreaks. It is thought that natural Ebola virus hosts are fruit bats of the Pteropodidae family. Transmission of Ebola
Close contact with the blood, secretions, organs or other bodily fluids of infected animals (eg. chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines) -> spread to humans Human-to-human transmission via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids Sexual transmission may be possible, but more surveillance data and more research is needed for proof.
Symptoms and diagnosis of Ebola virus disease The incubation period is 2 to 21 days. Humans are not infectious until they develop symptoms. Sudden onset of fever fatigue, muscle pain, headache and sore throat Vomiting, diarrhea, rash, symptoms of impaired kidney and liver function, and in some cases, both internal and external bleeding (e.g. oozing from the gums, blood in the stools). Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.
It can be difficult to distinguish EVD from other infectious diseases such as malaria, typhoid fever and meningitis. Confirmation that symptoms are caused by Ebola virus infection are made using the following investigations:
Antibody-capture enzyme-linked immunosorbent assay (ELISA) Antigen-capture detection tests Serum neutralization test Reverse transcriptase polymerase chain reaction (RT-PCR) assay Electron microscopy Virus isolation by cell culture
Vaccine development for Ebola virus Currently, there is no proven treatment methods for the Ebola virus disease. Yet, there are materials that are being evaluated in hope of potential treatments. No vaccines are now licensed to treat Ebola virus disease, but two potential vaccines are undergoing human safety testing.
6) Puzzle game!
Answers: 1. Sısǝuǝƃıxoʇ 2. Oʇınbsoɯ 6. ʇsoɥ 7. ɔıʇɐɯoʇdɯʎsɐ 11. ƃuıuıl
3. ɔıƃɐɥɹɹoɯǝɥ 4. ɹǝɔln 8. uoıʇɐqnɔuı 9. ʎʇıʇuǝ
5. ʇɔǝɹıp 10. ǝʌıʇɐʇǝƃǝʌ
7) References Christian Nordqvist. (2016, January 11). What Is Bacteria? What Are Bacteria?. Medical News Today. February 17, 2016, http://www.medicalnewstoday.com/articles/157973.php Dr. Ananya Mandal. (2013, February 12). What is a Virus?. News-Medical. February 17, 2016, http://www.news-medical.net/health/What-is-aVirus.aspx World Health Organization. (2016, January). Ebola Virus Disease. World Health Organization. February 18, 2016, http://www.who.int/mediacentre/factsheets/fs103/en/ Centre for Health Protection. (2016, February 29). Zika Virus Infection. Centre for Health Protection. March 2, 2016, http://www.chp.gov.hk/en/content/9/24/43088.html http://creately.com/diagram/example/hcqvfy502/Bacteria%20vs.%20Viruses %20 http://www.assignmentpoint.com/science/biology/virus-and-bacteria.html
Credits to: Miss. Chow Chi Yui (Teacher-in-charge) Shum Wing Zi 5B (Chairperson) Jocelyn To 4I (Editor in Chief) Venus Lai 4E (Committee member) Sandra Leung 4I (Committee member)
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