TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The bacterium belongs to a genus comprising Deinococcus, Bacillus, Microbacterium, Cellulosimicrobium, Methylobacterium, Sphingobacterium, Pseudomonas, Caldimonas, Paenibacillus, Gordonia, Rhodococcus, Stenotrophomonas, Novosphingobium, Sphingomonas, Flavobacterium, Sphingobium, Sphingopyxis, or Porphyrobacter. The sample is or derived from an environmental sample, preferably obtained or derived from soil, water, hot springs, marine environment, mud, wood, stone, moss, vegetal extract, lichen, biological material, sediment, peatlands, biofilm, industrial effluents, gas, sand, oil, sewage, animal or human dejection.    TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (Claimed): Preparation of the isolated bacterium comprises: providing a sample comprising bacteria; subjecting the sample to a cell destructing DNA damaging treatment; and isolating the bacterium which has the ability to live or grow in the presence of lignin, cellulose or xylan as a carbon source, from the treated sample. Preferred Method: In the method of producing bioenergy products or metabolites, the fermentation is performed using the bacterium. The method of producing bioenergy products or metabolites further comprises collecting the bioenergy products or metabolites. The cell-destructing DNA damaging treatment is a treatment that reduces by at least 2 log the bacterial titer in a culture of Escherichia coli, where the treatment comprises at least one irradiation, preferably a repeated sequential irradiation treatment including UV-irradiation (preferred), gamma-irradiation and/or X-ray-irradiation. The cell-destructing DNA damaging treatment comprises subjecting the sample to at least 2, preferably at least 3 UV treatments of 0.5-400, preferably 1-100 mJ/cm2 each, carried out at an interval of 1-8 hours. The step of subjecting the sample to a cell destructing DNA damaging treatment is performed in a solid culture medium. The steps of subjecting the sample to a cell destructing DNA damaging treatment and isolating the bacterium are performed sequentially in any order, or simultaneously. The method of selecting or identifying the bacterium further comprises modifying the identified or isolated bacteria or their DNA, biologically, genetically and/or chemically, to improve the viability, growth or functions of the bacterium.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The fermentable sugar is glucose, cellobiose, mannose, xylose, arabinose or galactose. EXAMPLE - Thermophilic bacteria selected for their resistance to UV rays from environmental samples (3 treatments of 4 mJ/cm2 with an interval of 4 hours) were inoculated on a solid minimal culture medium sterilized by autoclaving (15 minutes at 120 degrees C), and containing the carbon source of interest at 1% carboxymethylcellulose (CMC) or xylan. The minimal culture medium was made up of 3-(N-morpholino)propanesulfonic acid (MOPS) buffer solution at pH 7 and filtered, and comprises acid MOPS buffer (40 mM), ammonium chloride (20 mM), potassium hydroxide (10 mM), sodium hydroxide (10 mM), calcium chloride (0.5 mM), sodium sulfate (0.276 mM), magnesium chloride (0.528 mM), a solution of micronutrients at pH 5 (ammonium heptamolybdate (3 nM), boric acid (400 nM), cobalt(II) chloride (30 nM), copper sulfate (10 nM), manganese chloride (250 nM), zinc sulfate (10 nM)), a solution of vitamins at pH 4 (1 mg/l of D-biotin, niacin, pyridoxine-hydrochloride, thiamin-hydrochloride and vitamin B-12), a solution of dipotassium hydrogen phosphate at 5.7 mM, and a solution of iron(III) chloride at 20 mM in monosodium citrate. The conditions of anaerobiosis were ensured by the addition of a GENbag anaer (RTM: Atmosphere generators). After incubation in anaerobiosis at 45 degrees C for 4-5 days, the bacterium which uses CMC as its carbon source was isolated.