2.1 What bacteria are

Answer

The three options are:

• handwashing with soap
• vaccination to boost the immune system
• antibacterial drugs.

Answer

Diseases caused by bacteria in humans:

• Tuberculosis (TB) is caused by Mycobacterium tuberculosis and mainly affects the lungs. The classic symptom of active tuberculosis is a chronic cough with bloodstained sputum, fever and weight loss. This disease can spread to other people through respiratory secretions when patients with active TB cough, spit up their sputum or sneeze.
• Tetanus, also known as lockjaw, is characterised by muscle cramps and is caused by Clostridium tetani. This bacterium is commonly found in soil, dusts and manure. The bacteria can enter the body through a break in the skin and produce toxins that cause the muscle contractions. This disease is not spread from human to human.
• Typhoid fever is caused by Salmonella typhi serovar Typhi, sometimes abbreviated as Salmonella Typhi. Patients infected with it may experience mild to severe symptoms including fever, abdominal pain constipation and vomiting. This disease is spread through contaminated water or food.
• Pneumonia is an infection of the lungs. Some bacterial strains that can cause pneumonia include Streptococcus pneumoniae, Staphylococcus aureus and Klebsiella pneumoniae. Bacteria are the most common cause of pneumonia; viruses cause only about one third of cases of pneumonia in adults.

Diseases caused by bacteria in animals:

• Anthrax in cattle, sheep and goats is usually spread by contact with spores of Bacillus anthracis in the soil or from pastures. Animals present with weakness, staggering and bloody discharges, often rapidly leading to death – although sometimes sudden death of livestock is the first sign of the disease. Anthrax is a zoonotic disease, so it can also be passed from animals to humans.
• Salmonellosis in poultry, with Salmonella species causing disease in a wide range of birds including chickens and turkeys. Different species and serovars present differently, with common presentations being pullorum disease, fowl typhoid and fowl paratyphoid. Some strains of Salmonella in poultry can be passed to humans through the food chain.
• There are several species of Brucella which tend to present slightly differently in different species. The most common sign of brucellosis in livestock is abortion during the final trimester of pregnancy. Some species of Brucella are zoonotic.
• One of the most common aquatic diseases is Vibrio, which leads to massive mortality of cultured shrimp, fish and shellfish. Vibriosis (Vibrio illness) can be zoonotic, and Vibrio cholerae can cause cholera in humans.

Diseases caused by bacteria in plants:

• Bacterial leaf streak and black chaff are a major bacterial disease of wheat. The bacteria (Xanthomonas translucens) are seed-borne. Typical symptoms on the leaf consist of elongated, light brown lesions, several centimetres long, that are initially distinct but later coalesce to cover larger solid areas. Yield losses can be as high as 40%.
• Epidemics of rice bacterial blight caused by Xanthomonas oryzae have been observed in Asia, the western coast of Africa, Australia and Latin America. The early signs consist of streaks that spread from leaf tips and margins, eventually oozing a milky substance that dries into yellow droplets. Later on, leaves will die; infected seedlings die within a few weeks of infection.
• Bacterial canker mainly affects tomatoes (caused by the bacterium Clavibacter michiganensis), present worldwide. Infections result in wilting, defoliation, desiccation, skin cankers, significantly reduced fruit yield and quality, and ultimately plant death.