Micro-organisms Micro- organisms (or microbes) are literally microscopic organisms, which can only be seen properly with the aid of a microscope. These include bacteria, microscopic fungi (moulds) and protoctists. Although viruses, which are even smaller than bacteria, are generally considered to be non- living entities, they might also be included here as they are important disease-causing agents. Micro-organisms are the most numerous organisms in any ecosystem. There are about 159,000 known species, although this is thought to be less than 5% of the total in existence. There is vast genetic diversity among micro- organisms, which is not surprising as they began evolving over a billion years before land plants. This, coupled with their small size and reproduction, helps explain why micro-organisms, particularly bacteria, are the most widely distributed forms of life on the planet. While many are cosmopolitan species, others exist in habitats totally inhospitable to larger organisms. There are species of bacteria able to grow in hot springs up to 90° C, others live below freezing point in Antarctica, in soda lakes, anaerobic situations, and sites with high concentrations of metals, sulphur and other normally toxic compounds. Micro-organisms and people Micro-organisms are of immense importance to the environment, to human health and to our economy. Some have profound beneficial effects without which we could not exist. Others are seriously harmful, and our battle to overcome their effects tests our understanding and ingenuity to the limit. However, certain micro- organisms can be beneficial or harmful depending on what we want from them: saprophytic decomposers play an important role in breaking down dead organic matter in ecosystems, but these same micro- organisms can be responsible for food spoilage (rotting, going bad, going off) and subsequent illness.
Posted on: Thu, 27 Jun 2013 11:23:36 +0000
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