Phylogeny of cultivable heterotrophic bacteria derived from mixed colonies

Abstract

In nature, bacteria interact with each other in ways that do not occur in pure laboratory cultures. However, when bacteria are purified from environmental samples, the resulting colonies occasionally harbor diverse bacterial isolates, which we have termed 'associated isolates'. Bacteria were obtained from a freshwater lake along a euphotic gradient (100, 10 and 1% light penetration). Surprisingly, 76 of the 1196 resulting colonies harbored between 2 and 5 associated isolates (for a total of 168 associated isolates), and 121 of these associated isolates were recovered as pure cultures. A portion of the isolates (47/168) was non-viable after re-streaking, suggesting an inability to survive and reproduce in the absence of their associates. Partial sequencing of 16S rDNA revealed that these isolates were affiliated with Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria and Deinococcus-Thermus, and represented 26 genera. Colonies harboring associated isolates and those that harbored the largest number of isolates were primarily sampled from the 1% euphotic gradient. Significant differences in the distribution of associated isolates along the euphotic gradient suggest that environmental factors are driving these associations.KEY WORDS: Associated bacteria · Intracolony · Diversity · 16S rDNA · Freshwater Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 66: [95][96][97][98][99][100][101][102][103][104][105][106] 2012 through several stages of re-streaking to obtain pure cultures. Moreover, in many cases, when the physical separation of associated isolates is accomplished, one or all of them does not survive, suggesting their physiological inability to survive and reproduce in the absence of certain associations. The objective of this study was to provide insight into the phylogeny of isolates derived from an original colony. We looked for the presence of 2 or more different taxa from a single colony, performing a molecular and phylogenetic characterization of these isolates. These bacteria were collected from a natural freshwater lake in a tropical region. MATERIALS AND METHODS Study area and sampling siteCarioca Lake is a natural body of water situated in the middle of the Rio Doce Basin of Brazil. It is located in a Conservation Unit (Parque Estadual do Rio Doce, PERD, 19°29' 24'' to 19°48' 18'' S and 42°28' 18'' to 42°38' 30'' W) that is the largest remnant of Atlantic Forest in the state of Minas Gerais. Carioca Lake is meso trophic, round, shallow (11.8 m of maximum depth) and relatively small, with an area of 14.1 ha (Bortoluzzi et al. 2004, Bezerra-Neto et al. 2010). Sampling and bacterial isolationWater samples (500 ml) across a euphotic gradient in the limnetic (Lim) zone (Carioca Lake) were taken with Van Dorn bottles. The same water samples were used for physical and chemical measurements and bacterial culture. Collections took place on 23 June and 27 August 2007, which is the dry season. Sampling was conducted in the water column at diffe...

A survey on cultivable heterotrophic bacteria inhabiting a thermally unstratified water column in an Atlantic Rainforest lake

“…The present study detected 38 genera, which are widely distributed in the environment, having been isolated from soil, water, and clinical material ( Zwart et al, 2002 ; Berg et al, 2009 ; Humbert et al, 2009 ; Toh et al, 2010 ; Lee et al, 2011 ; Yang & Li, 2011 ; Soltan Dallal, Sharifi Yazdi & Avadisians, 2011 ; Costa et al, 2012 ). Among the genera, Aeromonas , Chromobacterium , Brevundimonas , Sphingomonas , Staphylococcus , Bacillus , Arthrobacter and Microbacterium predominated in one or both sampling months, with wide variation of their frequencies, except for Brevundimonas .…”

Environmental diversity of bacteria in a warm monomictic tropical freshwater lake

“…Similar studies are scarce in tropical environments (Humbert et al 2009;Ghai et al 2011;Costa et al 2012;Lima-Bittencourt et al 2014), and it is not certain that the results from studies in temperate regions can be extrapolated to tropical lakes. Research on lake bacteria have been carried out in the tropics targeting primary production (Sarmento 2012), methane dynamics (Sanseverino et al 2012;Conrad et al 2011), specific bacterial groups and their functions (Achá et al 2011;Souza et al 2012), antimicrobial resistance, and pathogens (Pontes et al 2009;Mwanamoki et al 2014) rather than bacterial taxonomic diversity.…”