Information Processing by Cyanobacteria During Adaptation to Environmental Phosphate Fluctuations

Abstract

Phosphate limited grown Anabaena variabilis has the capability of processing information about external phosphate fluctuations by means of interconnected adaptive events. Adaptive events are physiological processes that are characterized by two opposite manifestations, namely adapted states and adaptive operation modes. In adapted states the energy-converting constituents of the uptake system operate under the prevailing external conditions in a coherent manner with least energy dissipation. Adaptive operation modes take place when adapted states are disturbed by persistent changes in phosphate supply. In this mode the outcome of former adaptations to elevated phosphate levels guides the emergence of a new adapted state. The influence of antecedent adapted states on subsequent adaptations was studied experimentally and characteristic examples for such information processing are given. The theory of self-referential systems allowed analyzing these examples. For this purpose adaptive events had to be considered as elements of a communicating network, in which, along a historic succession of alternating adapted states and adaptive operation modes, information pertaining to the self-preservation of the organism is transferred from one adaptive event to the next: the latter "interprets" environmental changes by means of distinct adaptive operation modes, aimed at preservation of the organism. The result of this interpretation is again leading to a coherent state that is passed on to subsequent adaptive events. A generalization of this idea to the adaptive interplay of other energy converting subsystems of the cell leads to the dynamic view of cellular information processing in which the organism recreates itself in every new experience.

Rapid regulation of phosphate uptake in freshwater cyanobacterial blooms

“…The flow-force relationships were fitted using MLAB (Mathematical Modelling System, Civilized Software) and following Falkner et al (2006) and Aubriot et al (2011). The replot of J P versus log[P e ] was performed according to Thellier (1970) (Thellier plot), in which the slope corresponds to L P , expressed in µmol internal P mg −1 chl a h −1 The reliability of the method has been validated previously (Aubriot et al 2000.…”

“…where m > 1; m characterises (in addition to conductivity coefficients L and L P ) the dependence of the phosphate influx rate on the driving force during an adaptive process (Falkner et al 2006). A satisfactory fit (r 2 ≥ 0.9) was found for either m = 3 or 5 (see Table 2).…”

“…In the case of a community, the transient nonlinear behaviour may be the result of small specific differences in t R during adaptation, for example between filamentous cyanobacteria and bacterioplankton. In this short-term process, environmental information is stored in the newly acquired kinetic and energetic properties, which result in a novel adapted state , Falkner et al 2006. We hypothesise, therefore, that this initial response may mark the onset of more stable, long-lasting acclimated states (hours to days).…”

“…The linearity of the flow-force relation can be lost in the transient adaptive operation mode of uptake systems (Falkner et al 2006. Under these conditions, uptake behaviour during the self-organisation process can be modelled when nonlinear terms are added to Eq.…”

“…These organisms sense phosphate availability in the environment by histidine kinases and response regulators, which induce the expression of Pho regulon genes that encode high affinity P-binding proteins, alkaline phosphatase and other relevant proteins (Suzuki et al 2004, Schwarz & Forchhammer 2005, Juntarajumnong et al 2007, Pitt et al 2010. Additional complexities in phosphate regulation are related to changes in the kinetics and energetics of uptake systems during responses to sudden phosphate fluctuations , Falkner & Falkner 2003, Falkner et al 2006. When phosphate is available, the external nutrient is removed by phytoplankton down to low nanomolar threshold values ([P e ] A ), below which incorporation is not energetically possible (Falkner et al 1989.…”