Free-living means to obtain food on their own - they do not require a host. ANother name is saprophytic.


An organism, especially a fungus or bacterium, that derives its nourishment from dead or decaying organic matter. Also called saprobe.
https://uk.answers.yahoo.com/question/index?qid=200812060733...

obtaining food by absorbing dissolved organic material; especially : obtaining nourishment from the products of organic breakdown and decay <saprophytic fungi>
http://www.merriam-webster.com/dictionary/saprophytic

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Note added at 11 hrs (2014-12-23 00:28:43 GMT)
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Most heterotrophic bacteria are saprophytes, meaning that they obtain their nourishment from dead organic matter. In the soil, saprophytic bacteria and fungi are responsible for biodegradation of organic material. Ultimately, organic molecules, no matter how complex, can be degraded to CO2 (plus H2 and H2O). Probably no naturally-occurring organic substance cannot be degraded by the combined activities of the bacteria and fungi. Hence, most organic matter in nature is converted by heterotrophs to CO2, only to be converted back into organic material by autotrophs that die and nourish heterotrophs to complete the carbon cycle.
http://textbookofbacteriology.net/bacteriology_5.html