Naoyoshi Nishibori

Spatial and temporal variations in free polyamine distributions in Uranouchi Inlet, Japan

Abstract Polyamines are an essential component of living organisms that influence normal cell growth and development. Despite the possible importance of polyamines for marine microbial ecology, concentrations of polyamines in seawater are not well known. Using HPLC analysis with a cation exchange column and OPA reagent, we determined polyamine concentrations in seawater without carrying out desalting, concentration or derivatization steps prior to chromatography. In seawater collected from Uranouchi Inlet, putrescine and spermidine were the predominant polyamines, ranging from undetectable (N.D.) to 4.4 nM and N.D. to 2.8 nM, respectively. Though other polyamines were detected, the frequency of detection was much lower than that of putrescine and spermidine; concentrations ranged from N.D. to 0.9 nM for cadaverine, and N.D. to 3.2 nM for norspermidine. Norspermine and spermine were detected in only a few samples; their concentrations varied from N.D. to 3.2 nM and N.D. to 0.5 nM, respectively. These concentrations were higher in the summer.

Changes in polyamine levels during growth of a red-tide causing phytoplankton Chattonella antiqua (Raphidophyceae)

The polyamines, putrescine, spermidine, spermine and norspermine, were detected in both the free and conjugated fractions of Chattonella antiqua cells, and putrescine and spermidine were detected in the bound polyamine fraction. Of the free polyamines, spermidine was the most abundant throughout the growth period and increased strongly during the exponential growth phase. The free spermidine content increased linearly with growth rate. The maximum growth yield of C. antiqua was reduced in proportion to the concentration of methylglyoxal bis-(guanylhydrazone) (MGBG). The inhibition of growth by MGBG could be counteracted by the addition of spermidine to the medium. It is suggested that free spermidine plays a significant role in C. antiqua growth.

Occurrence of the polyamines caldopentamine and homocaldopentamine in axenic cultures of the red tide flagellates Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae)

The polyamines caldopentamine and homocaldopentamine were detected in axenic strains of Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae), respectively, as well as spermidine, the most abundant polyamine in both phytoplankton species. Trace amounts of putrescine, diaminopropane and norspermine were also detected in both species. Spermine was detected only from C. antiqua. These long linear polyamines are characteristic components of thermophilic bacteria. The detection from two species of Raphidophyceae indicates that the occurrence of long linear polyamines is not restricted to thermophilic microorganisms.

Changes in intracellular polyamine concentration during growth of Heterosigma akashiwo (Raphidophyceae)

Of the free, conjugated and bound forms of polyamines, the free form of spermidine was the most abundant polyamine in Heterosigma akashiwo throughout, the growth period except for the lag phase. Free spermidine content increased remarkably during the exponential growth phase and increased as the growth rate increased. The maximum growth yield of H. akashiwo was reduced by the addition of methylglyoxal bis-guanylhydrazone (MGBG) and the reduced growth yield could be counteracted by the addition of spermidine to the medium. It is concluded that spermidine plays a significant role in the growth of H. akashiwo. These results are similar to those obtained in Chattonella antiqua that belongs to same taxonomic Class as H. akashiwo.

Accumulation of an Aromatic Amine, β-Phenethylamine, in Root Nodules of Adzuki Bean Vigna angularis

Neuroactive aromatic amines acting on the central nervous system are widespread in the plant kingdom. We have previously found β-phenethylamine (β-PHA), one of the aromatic alkaloids, in root nodules of various annual legume crops. The present study was undertaken to determine the site of β-PHA accumulation within root nodules of the adzuki bean Vigna angularis. High concentrations of β-PHA were always detected in the alkaloid fraction of adzuki bean root nodules. Related aromatic amines such as tyramine, dopamine, and other β-PHA derivatives, which are found in various medicinal plants, were not detected in adzuki bean root nodules. The amounts of β-PHA in root nodules varied not only with the growth stage of the host plant, but also with nodule age; β-PHA levels increased with nodule development, but declined with nodule senescence. Adzuki bean nodules, after crushing with a grinding medium, were separated into bacteroids and a nodule cytosol fraction. A large amount of β-PHA was detected in the bacteroids, while a very small amount was prsent in the nodule cytosol fraction derived from plant cells. The bacteroids in the mature nodules contained considerably higher amounts of β-PHA than did those in immature or senescent nodules. The formation of β-PHA in root-nodule bacteria was then tested using eight strains of Rhizobiaceae (Rhizobium, Bradyrhizobium and Sinorhizobium), including a strain isolated from root nodules of field-grown adzuki bean plant. None of the cultured cells produced β-PHA in liquid media in the presence or absence of phenylalanine, a putative precursor of β-PHA. Nitrogen-fixing bacteroids within nodules are the cells uniquely differentiated from root-nodule bacteria. The present results suggest that β-PHA is formed associated with the differentiation of vegetative bradyrhizobia into nitrogen-fixing bacteroids with the plant host cells.