Activity and diversity of bacterial cells with high and low nucleic acid content

Abstract

In most aquatic environments, at least 2 subpopulations of bacterial cells can be discriminated by flow cytometry based on their nucleic acid content. Recent investigations have shown that the cells with a high nucleic acid (HNA) content have a higher cell-specific activity (CSA) cell than those with a low nucleic acid (LNA) content. In this study, the CSA and biomass-specific activities (BSA) of HNA and LNA cells from different aquatic ecosystems, including marine, brackish and freshwater, were investigated using radioactive leucine incorporation and cell sorting by flow cytometry. The genetic diversity of natural assemblages, HNA and LNA cells was investigated using the SSCP (PCR single-strand conformation polymorphism) method. Data showed that both CSA and BSA of HNA cells were always significantly higher than CSA and BSA of LNA cells. In addition, HNA cells had a dominant contribution to the production of the total community (77 to 98%). For the different samples, the SSCP fingerprints from the natural assemblage and from the 2 sorted fractions were not significantly different. This clearly suggests that HNA and LNA subpopulations were composed by the same dominant species and, thus, confirms an important heterogeneity of physiological states within most natural populations.

Marine bacterial community structure resilience to changes in protist predation under phytoplankton bloom conditions

“…However, contrasting results have been reported, with some studies in coastal sites showing that the HNA and LNA populations are different, whereas others found similar taxonomic composition (Servais et al, 2003;Longnecker et al, 2005). Moreover, it is possible that the HNA cells growing (and then being grazed) in our experiment belonged to a limited number of taxa responding to the phytoplankton bloom by rapid growth, thus overriding the effect of the heavy HNF bacterivory; this is a life strategy suggested for freshwater bacteria of the genus Limnohabitans (Šimek et al, 2014).…”

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

“…It was reported that coastal seas had a lower proportion of LNA bacteria, such as on a transect from Delaware to the Sargasso Sea (35%), or the Grand Banks (22-42%) (Li et al 1995;Li and Dickie 2001). In contrast, there was a higher proportion of LNA bacteria found in the coastal Canet lagoon (57%; Servais et al 2003), eastern Mediterranean Sea (65%), North Atlantic (64%; Li et al 1995) and the Gulf of Mexico (62%; Jochem et al 2004). In comparison, only a few reports are available on LNA and HNA bacteria in freshwater environments (Ni et al 2015;Read et al 2015).…”

Distribution of HNA and LNA bacterial groups in the Southwest Atlantic Ocean

“…The HNA bacteria were considered the most active members of a given community while LNA were regarded as inactive, dead or dormant cells (17,26,27). HNA and LNA were also considered to be members of the same phylotypes (11,38). However some have demonstrated that LNA are different phylotypes from HNA cells (12,31,45) and that indeed LNA can be responsible for a significant portion of total heterotrophic metabolism (1,22,31,34,45), all observations from oligotrophic systems as open oceans.…”