A comparative study of the cytometric characteristics of High and Low nucleic‐acid bacterioplankton cells from different aquatic ecosystems

Abstract

Flow cytometry has revealed the existence of two distinct fractions of bacterioplankton cells, characterized by high and low nucleic acid contents (HNA and LNA cells). Although these fractions seem ubiquitous in aquatic systems, little is known concerning the variation in the cytometric parameters used to characterize them. We have performed cytometric analyses of samples from a wide range of aquatic systems to determine the magnitude and variability in the cytometric characteristics of HNA/LNA. We show that neither group is associated to a fixed level of fluorescence and of light scatter. Rather, the relative position of HNA and LNA in the fluorescence versus side scatter cytograms varies greatly, both within and among ecosystems. Although the cytometric parameters of both groups tend to covary, there is often uncoupling between the two, particularly in light scatter. Our results show that, although the basic HNA/LNA configuration is present in most samples, its cytometric expression changes greatly in different ecosystems and along productivity gradients. The patterns in cytometric parameters do not support the simple, dichotomous view of HNA and LNA as active and inactive cells, or the notion of two distinct and independent communities, but rather suggest that there may be cells that are intrinsic to each fraction, as well as others that may exchange between fractions.

Geographic distribution pattern of low and high nucleic acid content bacteria on a river-catchment scale

“…3b). In addition, because LNA and HNA were clearly distinguishable from cytometric parameters (FL1 and SSC), the derived variables FL1 HNA : FL1 LNA and SSC HNA : SSC LNA were used to represent the degree of the relative distances between LNA and HNA in FCM (Bouvier et al 2007). The results showed that the relative distance of FL1 between these two subgroups was significantly higher than that of SSC (Fig.…”

“…At least two major groups of bacteria, namely those with low and those with high nucleic acid content, can be distinctively characterised by FCM after staining with DNA-binding dyes (Bouvier et al 2007;Wang et al 2009). They were originally classified as 'Group I cells' and 'Group II cells' (Li et al 1995), then as 'low nucleic acid-content (LNA) bacteria' and 'high nucleic acid-content (HNA) bacteria' (Lebaron et al 2001).…”

“…They were originally classified as 'Group I cells' and 'Group II cells' (Li et al 1995), then as 'low nucleic acid-content (LNA) bacteria' and 'high nucleic acid-content (HNA) bacteria' (Lebaron et al 2001). This classification was based on the different fluorescence intensity and side scatter signal of the cells as detected by FCM, where fluorescence intensity was regarded as an indicator of intracellular nucleic acid content (genome size and the number of genome copies) and side scatter as an index of cellular morphological characteristics (size, internal granulosity and cytoskeletal proteins; Bouvier et al 2007). Although this classification is method-specific for FCM, it has been widely applied in different research fields (Bouvier et al 2007;Van Wambeke et al 2011;Huete-Stauffer and Morán 2012).…”

Microbial Ecology of Lake Kivu

“…Bouvier et al 2007 ) . The general pattern that emerges from the literature is that HNA cells appear to be not only larger cells but also more active cells, with high speci fi c metabolism and growth, and that changes in total bacterial abundance are often linked to changes in this fraction (Lebaron et al 2001 , but see Jochem et al 2004 ;Bouvier et al 2007 for other possible scenarios on this topic).…”

High-resolution imaging of pelagic bacteria by Atomic Force Microscopy and implications for carbon cycling

“…Electronic counters might treat conjoint bacteria as a single, larger cell. Distinguishing high and low DNA cells in pelagic bacterial populations (Bouvier et al, 2007;Falcioni et al, 2008) by flow cytometer might also be affected by low DNA conjoint heterotrophic bacteria being treated as a single high DNA cell. Further, AFM can provide a wealth of information on the bacterium's microscale ecology that goes well beyond the initial intent to know the cell volume and C content.…”