Theory question 101
Microorganisms and Health(a) (i) List two diseases each of plants and animals caused by bacteria (ii) State three ways in which bacteria are useful.
(b) State three methods by which mosquitoes can be controlled and state the reason for each method.
(c) Describe an experiment to demonstrate the presence of bacteria under the finger nails
Show the model answer
(a)(i) Plants (two): soft rot of vegetables (e.g. carrot, yam), bacterial blight of cassava, bacterial wilt of tomato, crown gall, black arm of cotton
Animals (two): tuberculosis, cholera, typhoid, tetanus, gonorrhoea, anthrax, pneumonia
(ii) Any three: nitrogen fixation and nitrification (soil fertility); decay of dead matter/recycling nutrients; sewage treatment; making foods (yoghurt, cheese, vinegar); making antibiotics/vaccines; digestion of cellulose in ruminants; tanning and retting
(b) Any three with reasons: drain stagnant water/clear bushes and cans – removes breeding sites; spray oil/kerosene on water – suffocates larvae; introduce larva-eating fish (Tilapia/Gambusia) – biological control; spray insecticides – kills adults; use nets/screens – prevents bites
(c) Prepare sterile nutrient agar in petri dishes; scrape dirt from under the finger nails with a sterile pin/loop and streak it on one plate; leave a second plate unopened as control; seal and incubate (warm place, about 37 °C) for 2–3 days
Result: colonies of bacteria appear on the inoculated plate but not on the control; so bacteria are present under finger nails
Always describe a control plate in a microbiology experiment.