ORIGINAL PAPER Characterization of aerobic heterotrophic bacteria in cold and nutrient-poor freshwater ecosystems Roy Mackenzie • Javier A. Barros • Miguel A. Martı ´nez Received: 23 September 2010 / Accepted: 10 March 2011 / Published online: 23 March 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Aerobic heterotrophic bacteria present in the surface water of three cold and nutrient-poor lakes in the Chilean Patagonia (Alto Reino, Las Dos Torres and Venus) were analysed for genetic similarity and metabolic diver- sity using 16S ribosomal DNA and the Biolog EcoPlate TM system, respectively. Bacterial fingerprints of water sam- ples in enriched and non-enriched nutrient broth demon- strated a [ 50% fingerprinting similarity between the lakes. Metabolic activity was also similar. However, the Biolog EcoPlate TM system carbon substrates revealed functional diversity. Lake Las Dos Torres showed the most finger- printing similarity between enriched and non-enriched cold water samples. The amounts of living and viable bacteria were also higher in this lake’s water sample, suggesting a predominance of facultative oligotrophic groups. DNA sequencing analysis demonstrated the presence of phylum Bacteroidetes in Lake Alto Reino; phyla Bacteroidetes and Gammaproteobacteria in Lake Las Dos Torres; and phyla Bacteroidetes, Alphaproteobacteria, and Gammaproteo- bacteria in Lake Venus. Although each lake had a unique bacterial community structure, the different bacterial groups may be performing similar metabolic functions, given the similarity in extreme environmental conditions. Keywords Cold  Nutrient-poor  Freshwater  Bacterial communities  Bacterial diversity Introduction In cold and nutrient-poor aquatic ecosystems, bacteria share physiological properties that enable them to survive in the nutritional and thermal conditions imposed by the environment (Priscu and Christner 2003). Steven et al. (2007) indicated that the characterization of microbial diversity improves the understanding of ecosystem func- tion and the role of bacterial populations. Moreover, Mit- eva et al. (2004) suggested that the enzymatic diversity observed in bacteria isolated from cold nutrient-poor environments could be explained as an adaptation in order to survive in these extreme conditions. Furthermore, Gro- udieva and Kambourova (2004) demonstrated catalytic activity below water freezing point of enzymes of psy- chrophilic and psychrotolerant bacteria isolated from the Arctic Ocean. Studies using cultivation-dependent methods provide insight into the physiological potential of isolated organ- isms in extreme ecosystems (Ward et al. 1990), but not on the composition of microbial communities in natural environments (Nocker et al. 2007). Given the disparity between in situ and culture–recoverable diversity, it is difficult to assess the representativeness of isolated mem- bers in the total bacterial community (Ward et al. 1990). Orphan et al. (2000) demonstrated that through the use of culture-independent molecular methods, cultivable micro- organisms taken from natural environments represent less than 10% of the existing microbial community. Neither methodology provided information relative to the meta- bolic potentials of bacterial groups, nor revealed the adaptive responses to environmental changes. The Chilean Patagonian lakes are of glacial origin and some of them were characterized by Campos (1984) and Soto (2002). They described them as having similar R. Mackenzie  J. A. Barros  M. A. Martı ´nez (&) Departamento de Microbiologı ´a, Facultad de Ciencias Biolo ´gicas, Universidad de Concepcio ´n, Casilla 160-C, Concepcio ´n, Chile e-mail: mimartin@udec.cl 123 World J Microbiol Biotechnol (2011) 27:2499–2504 DOI 10.1007/s11274-011-0718-2