1. What are the dangers of pathogens, which live in the environment? In your answer, use specific examples from at least one environment (soil, food and water, or air).
A pathogen, like fungus or bacterium, is an agent that causes deceases, particularly living microorganisms. The natural environment (soil, food and water, or air) in most cases contains nutrients but some microorganisms have taken advantage of these environs to live on the nutrients already available. However, humans are constantly exposed to various micro organisms in the ecology, tiny portion are pathogens and these organisms cause deceases and infections. These pathogens bring about waterborne deceases like diarrhea, eye, nose and throat infections meningitis, heart deceases and lung infection among others (Lucas and Campbell, 1998). Microorganisms in the soil significantly reduce the quality and yield of or in vegetable. In severe cases may cause food poisoning, which may in turn result to death. These organisms in the air often bring about allergies and asthma or even infectious illnesses like measles and chicken pox. Finally, tainted food may cause a number of illnesses like arthritis and kidney illnesses (Lucas and Campbell, 1998).
2. Describe the potential effects of climate change on the global incidence and severity of infectious diseases.
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Infectious deceases are the deceases that are or can be contagious and can be transferred via various medium. Lucas and Campbell (1998) that unusual and severe climatic conditions can change severity of a number of infectious deceases and their global occurrences. These deceases often are very small and their temperature and levels of fluids is determined by the climate. A possibility is that these pathogens are rapidly transmitted in accordance to various factors of the climate like humidity. An example is that “in Scotland, campylobacter infections are characterized by short peaks in the spring” says Lucas and Campbell (1998). Malaria among others is also sensitive to change of climate this is because the maturity of these parasites in the mosquitoes needs 18 degrees approximately, (Lucas and Campbell, 1998). Therefore, changes in the temperature, humidity and other climatic factors may drastically affect the transmission of deceases. Additionally that seasonal fluctuation of these deceases through the year may indicate a direct link of the infectious deceases to change in the climate.
3. A bacterium (species A) is suspected of causing leaft blight of potatoes. Explain the proess that you would use to obtain proof of pathogenicity. (Species A is able to be grown on artificial media)
Symptoms of potato blight are light to dark green spots and form cotton like white moldy growth. Koch introduced a method to identify pathogenicity which he called Koch’s Postulates that comprised of three rules; “The suspected causal organism must be constantly associated with the disease, secondly, must be isolated from an infected plant and grown in pure culture. The third point is, when a healthy susceptible host is inoculated with the pathogen from pure culture, symptoms of the original disease must develop. Lastly, the same pathogen must be re-isolated from plants infected under experimental conditions” (Kok and Victoria, 1999). First step is to cut six sections of 1cm from the infected leaf tissue, then sterilize the tissue surface and place these samples in a humidity chamber for five days, ensure that they are in plastic bags. Finally examine these leaf tissues for fungal spores then place the spores in a Petri dish containing agar medium and incubate at room temperature for about a week.
4. Describe host-pathogen relationships in plant disease. In your answer, consider transmission, infection, and host defenses
The environment has a variety of potential pathogens that confront plants constantly through a process referred to as inoculation. Amino acids, sugars and mineral salts generated from seeds, leaves and roots through the normal process of plant growth may trigger the sprouting of pathogens within the phyllosphere (leaves), rhizosphere (roots) and spermosphere (seeds)” (24). The pathogen must invade the host’s tissues through a process referred to as infection, for a disease to develop. Consequently, the pathogen starts to grow and create an intimate relationship with the host through a process referred to as “colonization of the host” (Lucas, G. and Campbell, 1998).
There are three ways through which pathogens enter the host: through wounds, direct penetration via outer layers of the tissue and through natural openings (Lucas, G. and Campbell, 1998). For instance, nematodes enter plant cells by piercing using stylets, fungi spores may enter through openings like hydathodes and stomates and insect vectors inject viruses into plants through the feeding process.
The pathogens may not cause diseases sometimes due to incompatible relationship. However, as they continue to develop in plants, certain symptoms will start to occur depending on the host plant and the pathogen involved.
The plant can protect itself from pathogenic invasion through passive and active defenses. Passive defenses entail physical and chemical barriers that guard the plant. Physical barriers are properties of the plant such as thick cuticles and cells walls while chemical barriers are chemicals compounds like phytoanticipins, quinines and phenols. On the other hand, active defenses entail specific and non-specific elicitors (Lucas, G. and Campbell, 1998).
5. How have agricultural practices have altered plant pathogens and pathogenesis? In your answer, consider infection, transmission and host range
Agricultural methods have altered plant pathogens and pathogenesis in several ways; these can be either by promoting the genesis and growth of pathogens on the plant or by inhibiting this. These are practices that are done as routine management of the plant and not to necessarily promote or control pathogens or pathogens (Kok and Victoria, 1999). This can be by; creating a condusive environment for the pathogens, providing necessary nutrients for their survival and by providing the mode of transmission and a host range that supports survival. Such practices include crop rotation systems, soil tillage, residue management in mixed farming and monoculture.
Where crop rotation is used pathogens and pathogenesis can be controlled by ensuring limitations of the host range while soil tillage provides favorable hibernation habitats for pathogens but it destroys the hyphae lowering the chances of survival of fungi such as R.solani.
Monoculture, which involves planting one type crop on a large piece of land over a long period can promote pathogenesis. This is because incase a certain strain of a pathogen infects one plant the entire population could affected due to similarities genetic makeup.
6. Explain why nobody needs to fertilize an old growth rainforest.
Plants in a rainforest are able to acquire nutrients they need through the process of decomposition which is the process through which dead material; such wood and leaves; excrement are quickly recycled by termites, bacteria and fungi to produce nutrients like iron, phosphorus and calcium which are then absorbed by plant via roots. This process ensures that nutrients are returned to the system. Mineral dust, which refers to dust from the desert, loaded in the atmosphere by human activities supplies nutrients such as oxides and carbonates to the rain forest. For instance, the Sahara desert is a major source of mineral dust for the Amazon forest. Another source of nutrients is biomass burning through which large amounts of carbon dioxide which have been stored over a long period are rapidly released into the atmosphere which is then used by plants in the rainforest (Kok and Victoria, 1999).
7. A new antibiotic has been isolated from nature. Explain how you would screen it against Staphylococus aureus.
Screening a new antibiotic against staphylococus aureus can be facilitated with the search engine across Antimicrobial Peptide Database (APD). This database is made of all the natural antimicrobial peptides (AMPs) ranging from animals to plants and from fungi to bacteria. This is done with the aim of identifying the “novel templates against methicillin-resistant staphylococcus aureus (MRSA) and by screening for instance, 30 peptides selected from the APD” (Menousek, Mishra and Hanke, 2012: 402).
The peptides should be short, cationic and cysteine-free and serve as a representation of candidates from various biological sources like fish, arachnids, bacteria, and amphibians. From such an experiment, it can be established whether the antibiotic can be used against Staphylococus aureus if they apply effective antimicrobial action against an isolate of MRSA USA300 (Menousek, Mishra and Hanke, 2012).
8 .Describe how a new biocontrol agent would be studied/ screened for field application.
Biological control (biocontrol) is defined as the study and utilization of natural enemies to control the population and numbers of pests (Kok and Victoria, 1999). The pests are regulated by using pathogens, predators and parasites, collectively referred to as control agents.
To study/ screen a new biocontrol agent for field application, the following steps apply:
- Establish if the pest is appropriate for biological control because not all pests can perform this task.
- Select appropriate and effective biocontrol agents for pests believed to be suitable for biocontrol.
- Conduct safety tests to make sure that the prospective agents will not turn out to be pests but only feed on the target pests (Kok and Victoria, 1999).
- Initiate systems to bring up the biocontrol agents to ensure that there is sufficient supply in case of approval for use.
- If approved for release, carry out field establishment studies concerning the biological control agents.
- The last step is carrying out evaluation surveys to establish the effectiveness of the agents in target pest control and find out if they have affected non-target species (Kok and Victoria, 1999).
9 .Describe three uses of DNA probes in biotechnology
In the recent past DNA probes have been used to discover and name pathogens which assist in identifying genetic plant infection and to ensure that plants are kept free from pathogens. This is done through matching the genetic makeup of different pathogens which makes the process of finding pesticides simpler. In addition to this DNA probes in generating better plants by modifying the genetic makeup of single cell by creating proteins that cannot be found in a plant; this in turn influences a plant abilities such as resistance to drought and infections. This modification is an organisms DNA is called recombination. Lastly, a recombinant DNA after modification enables the plant to fix nitrogen this is achieved by inserting the nitrogen fixing bacteria into the plant which means that the bacteria which do that are not necessary (Kok and Victoria, 1999).
10. Describe botulinal cook concept. Does this ensure that the food is sterile? Justify your answer.
The concept of botulinum cook entails cooking food especially meat a high temperature. The minimum temperature should be 121°C and the food has to cook a period not less than 3 minutes. The aim of this process is to minimize the likelihood of clostridium botulinum spores that cause botulism, a rigorous form of food poisoning caused by ingesting toxins generated by C. clostridium. It is important that foods preserved in airtight containers and rich in low acid (more than pH 4.5) undergo the process to avoid the risk on contamination. Such foods include mushrooms, meats, poultry and other forms of vegetables apart from tomatoes (Benedict, 1980).
Botulinum cook ensures that food is sterile because heating at such a high temperature kills many germs. Through this process, the entire contaminating bacteria together with their spores are destroyed. Such treatment inactivates bacteria that are normally resistant to heat at a low temperature, making the food safe (Benedict, 1980).
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