Heterotrophic bacteria from an extremely phosphate‐poor lake have conditionally reduced phosphorus demand and utilize diverse sources of phosphorus

Abstract

Summary Heterotrophic Proteo- and Actinobacteria were isolated from Lake Matano, Indonesia, a stratified, ferruginous (iron-rich), ultra-oligotrophic lake with phosphate concentrations below 50 nM. Here, we describe the growth of eight strains of heterotrophic bacteria on a variety of soluble and insoluble sources of phosphorus. When transferred to medium without added phosphorus (P), the isolates grow slowly, their RNA content falls to as low as 1% of cellular dry weight, and 86-100% of the membrane lipids are replaced with amino- or glycolipids. Similar changes in lipid composition have been observed in marine photoautotrophs and soil heterotrophs, and similar flexibility in phosphorus sources has been demonstrated in marine and soil-dwelling heterotrophs. Our results demonstrate that heterotrophs isolated from this unusual environment alter their mac-romolecular composition, which allows the organisms to grow efficiently even in their extremely phosphorus-limited environment.

Freshwater Bacteria Release Methane as a By-Product of Phosphorus Acquisition

“…4). This strain has been shown to decrease RNA content and replace its phospholipids with amino-and glycolipids when P is limited, so the cells may increase their P content without necessarily altering the growth yield (38). As the MPn concentration increases, the cell yield and total methane production also increase, suggesting that availability of additional P promotes additional growth, as expected (Fig.…”

“…Heterotrophic bacteria isolated from Lake Matano were recently shown to utilize a diverse array of P sources, including 2-AEP (Table 1) and to make large changes in the RNA content and lipid composition of the cells when P starved (38). To assess the probability of methane production from MPn degradation in Lake Matano surface water, reads mapping to genes encoding the C-P lyase pathway (Fig.…”

“…Pantoea ananatis ϩ ϩ a All strains listed were isolated from water collected from Lake Matano, Indonesia, as described previously (38). The ability to use methylphosphonate (MPn) or 2-aminoethylphosphonate (2-AEP) was assessed by monitoring growth in NBRIP medium with MPn or 2-AEP supplied as the sole phosphorus source at a concentration of 0.2 mM.…”

“…This P limitation may result in microbial acquisition of P from a wide variety of sources (38), ultimately leading to release of organic by-products such as methane.…”

“…However, in severely P-limited systems, demethylation of P-containing compounds may also contribute to surface water methane production. Because Lake Matano has less than 50 nM total P i in the surface water (37), planktonic organisms there must be capable of immediate uptake and utilization of P in any available form (38). Both physiological experiments with isolates and bioinformatics analysis of metagenomic data indicate that heterotrophic bacteria in Lake Matano surface water are capable of producing methane as a by-product of acquisition of P from phosphonate compounds.…”