Click on a number in the grid to see the clue or clues for that number.
Complete the crossword, then click on "Check" to check your answer. If you are stuck, you can click on "Hint" to get a free letter.

1			2				3									4
													5
					6					7
																		8
							9
													10
11
																12
							13				14
						15
		16
										17
18

 Check 

Across: 3. a swelling on the root of a leguminous plant containing nitrogen-fixing bacteria (4,6) 7. metal instrument used to transfer micro-organisms; easily sterilised by heating to red heat (4,4) 9. potentially fatal disease characterised by severe diarrhoea; caused by water-borne bacteria (7) 10. compound containing the chemical element nitrogen; absorbed from the soil solution by plant roots. (7) 11. introduction of a micro-organism to an environment containing the requirements for its growth (11) 14. microscopic organisms, normally unicellular, that lack chlorophyll; many types feed on and decompose organic waste (8) 15. unwanted micro-organism that has gained access to a culture or food medium (11) 16. organic waste material containing faeces, urine, soap, food fragments, paper etc. (6) 17. liquid containing waste discharged from a sewage works (8) 18. partly treated sewage rich in decay bacteria (9,6)

Down: 1. micro-organisms that bring about denitrification (12,8) 2. procedure adopted to prevent unwanted micro-organisms from entering and contaminating culture plates and tubes. (7,9) 4. bacterial spore surrounded by a thick coat that enables it to survive unfavourable conditions (9) 5. toxic form of alcohol (8) 6. result of the rapid growht of populations of microscopic water plants (5,5) 8. apparatus used to serilise glassware and chemicals (9) 12. chemical compound containing nitrogen that is present in foods such as meat and soya bean (7) 13. tiny reproductive unit of micro-organisms such as fungi (5)