I. Choose the appropriate preposition

When most people think of bacteria, they think of disease-causing organisms, like/as/of the Streptococcus bacteria, which were isolated from/out/off a man with strep throat. While pathogenic bacteria are notorious of/about/for such diseases as cholera, tuberculosis, and gonorrhea, such disease-causing species are a comparatively tiny fraction of the bacteria like/as/in a whole.

Bacteria are so widespread that it is possible only to make the most general statements about/of/for their life history and ecology. They may be found on/at/in the tops of mountains, the bottom of the deepest oceans, on/at/in the guts of animals, and even in the frozen rocks and ice of Antarctica. One feature that has enabled them to spread so far, and last so long is their ability to go dormant on/for/at an extended period.

II. Complete the following passage by choosing the correct prepositions from the list below to fill in the gaps

As (x3) by (x2) from (x2) in (x2) into (x2)

Like of on (x2) since to without

Most bacteria may be placed (1)_____ one of three groups based (2)_____ their response (3)_____ gaseous oxygen. Aerobic bacteria thrive (4)_____ the presence of oxygen and require it (5)_____ their continued growth and existence. Other bacteria are anaerobic, and cannot tolerate gaseous oxygen, such (6)_____ those bacteria which live in deep underwater sediments, or those which cause bacterial food poisoning. The third group are the facultative anaerobes, which prefer growing in the presence of oxygen, but can continue to grow (7)_____ it.

Bacteria may also be classified both by the mode by which they obtain their energy. Classified by the source of their energy, bacteria fall (8)_____ two categories: heterotrophs and autotrophs. Heterotrophs derive energy (9)_____ breaking down complex organic compounds that they must take (10)_____ (11)_____ the environment -- this includes saprobic bacteria found in decaying material, (12)_____well (13)_____ those that rely (14)_____ fermentation or respiration.

The other group, the autotrophs, fix carbon dioxide to make their own food source; this may be fueled (15)_____ light energy (photoautotrophic), or (16)_____ oxidation of nitrogen, sulfur, or other elements (chemoautotrophic). While chemoautotrophs are uncommon, photoautotrophs are common and quite diverse. They include the cyanobacteria, green sulfur bacteria, purple sulfur bacteria, and purple nonsulfur bacteria. The sulfur bacteria are particularly interesting, (17)_____ they use hydrogen sulfide as hydrogen donor, instead (18)_____ water (19)_____ most other photosynthetic organisms, including cyanobacteria.

LISTENING COMPREHENSION

I. You are going to hear a fragment of a lecture about the best-known prokaryote Escherichia coli (E. coli). Before listening study the following measurements and discuss the meaning of the words in the box below with your classmates or teacher

µm – micrometer = 1/1000 mm = 10^-6 m (one millionth of a meter)

nm – nanometer = 1/1000 µm = 10^-9 m (one billionth of a meter)

µm³ – cubic micrometer

10^-12g (one-millionth of one-millionth of a gram) = 0,0000000000001g

humble intestinal tract length approximately weight tiny bundle

magnified human dimensions nonetheless favorable under the conditions whereas rapid division

immense nutritional requirements health hazard extensive precautions differing genet ic strains potassium (K)

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Vocabulary notes	\|	II. Listen to the tape and fill in the gaps with the correct figures concerning the structure of E. coli

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