Irgasan-induced pigmentation in Serratia marcescens and Pseudomonas aeruginosa.

Two irgasan-resistant micro-organisms (P. aeruginosa and S. marcescens) were used to study the effects of various antibiotic and chemotherapeutic agents on pigment production. These agents included streptomycin, thallium acetate, polymyxin B, hexachlorophene, irgasan, prodigiosin and DMSO (dimethyl sulphoxide). Only irgasan, compared to other drugs and membrane-active agents showed the unique property of inducing pigmentation in both P. aeruginosa and S. marcescens, i.e. prodigiosin in S. marcescens and pyocyanin in P. aeruginosa.     

Glucose-6-phosphate dehydrogenase alloenzymes and their relationship to pigmentation in Serratia marcescens

A comparative study of environmental and clinical isolates of Serratia marcescens was undertaken with regard to glucose-6-phosphate dehydrogenase (G6PD) electrophoretic mobility and the production of prodigiosin. Two electromorphs of G6PD with electrophoretic mobilities of 0.22 and 0.30 were detected. G6PD electrophoretic type showed a good correlation with the ability to produce prodigiosin.     

Phosphate inhibition of secondary metabolism in Serratia marcescens.

The synthesis of prodigiosin by non-proliferating cells of Serratia marcescens was examined in the presence of a wide range of concentrations of inorganic phosphate (Pi). A high elevation of pigment formation was obtained at less than or equal to 0.3 mM, and a broader but much lower elevation was obtained at 10 to 250 mM Pi. The synthesis of two immediate precursors of the pitment also was inhibited by Pi. The mechanism of action of Pi did not involve changes in pH or accumulation of the trace metal nutrient iron or zinc. Inhibition was most pronounced when Pi was added to the induction system before the onset of pigment formation. The inhibitor also diminished the burst of alkaline phosphatase activity that occurred in the period between the start of induction and appearance of prodigiosin.     

Flagellar variation in Serratia marcescens is associated with color variation.

The pigmented enterobacterium Serratia marcescens, an opportunistic pathogen, shows a striking variation of its red color. Different strains differ greatly both in color and in the frequency with which they produce color variants. Within a strain, the variations occur at constant rates and are reversible. During an investigation of this phenomenon we observed that variation of a 39-kilodalton protein in S. marcescens 274 is closely associated with color variation. Using antibodies to this protein we identified it as being a component of the bacterial flagella. Variation of surface proteins often provides an organism with alternate offense-defense strategies for survival in a challenging environment. The pigment, in association with flagella, may provide such a function for S. marcescens.     

Glucose-6-phosphate dehydrogenase alloenzymes and their relationship to pigmentation in Serratia marcescens.

A comparative study of environmental and clinical isolates of Serratia marcescens was undertaken with regard to glucose-6-phosphate dehydrogenase (G6PD) electrophoretic mobility and the production of prodigiosin. Two electromorphs of G6PD with electrophoretic mobilities of 0.22 and 0.30 were detected. G6PD electrophoretic type showed a good correlation with the ability to produce prodigiosin.     

Induction of pigmentation in nonproliferating cells of Serratia marcescens by addition of single amino acids

Addition of casein hydrolysate to suspensions of washed, nonpigmented, nonproliferating Serratia marcescens incubating at 27 C induced biosynthesis of prodigiosin. Four amino acids of casein hydrolysate, dl-aspartic acid, l-glutamic acid, l-proline, and l-alanine caused formation of pigment when added individually. dl-Ornithine also was effective. Optimal concentrations for maximal pigmentation were 5 to 10 mg/ml; at these high concentrations, d-serine also induced biosynthesis of some prodigiosin. dl-Alanine and -ornithine were as effective as the l-iosomers, but l-glutamic acid and l-proline gave better responses than their racemic mixtures. Kinetics of prodigiosin biosynthesis after addition of dl-alanine (20 mg/ml) were similar to those of cells suspended in 0.2% casein hydrolysate. The other amino acids were less effective. Addition of 5 mg of dl-alanine or casein hydrolysate per ml to minimal medium increased by 30% the amount of prodigiosin formed by growing cells after incubation for 7 days at 27 C. Cultures grown for 7 days at 27 C in 0.2% casein hydrolsate formed more prodigiosin than did suspensions of nonproliferating cells containing individual amino acids or casein hydrolysate. However, more pigment was produced by cells suspended in l-alanine (5 mg/ml) or l-proline (10 mg/ml) than when suspended in 0.4% natural or synthetic casein hydrolysate. Filtrates from suspensions of nonproliferating cells forming pigment in l-proline induced more rapid formation of prodigiosin, but filtrates from suspensions in dl-alanine did not. The data supported the hypothesis that pyrrole groups of prodigiosin may be synthesized from 5-carbon amino acids such as proline, ornithine, aspartic, and glutamic acids, but the role of alanine is unknown.     

The effect of the cultivation conditions on the growth and pigmentation of Serratia marcescens

The influence of cultivation conditions on the growth and pigmentation of S. marcescens was studied. The cultures under study grew in media containing glycerin, glucose or acetate and organic or mineral nitrogen. Pigment formation occurred in a medium with organic nitrogen and glycerin or acetate, but not glucose. Sodium chloride inhibited the growth of cultures, but at a concentration not exceeding 4-5% increased the accumulation of prodigiosin. Prodigiosin was accumulation by the culture growing at 28 degrees C, while at 37 degrees C no accumulation of the pigment occurred. The illumination of the growing culture with visible light decreased the intensity of its pigmentation. Prodigiosin apparently plays an important role in the metabolism of S. marcescens and is linked with the energy exchange of the cell.     

Cation transport in Serratia marcescens and Serratia marinorubra

The sodium, potassium, and magnesium ion contents of Serratia marcescens and those of its salt-tolerant relative, S. marinoruba, were determined by atomic-absorption spectrometry. The intracellular K(+) and Mg(2+) contents of both microorganisms were found to be dependent on the ionic strength of the growth or suspending medium. The Mg(2+) content of S. marinoruba was generally greater than that of S. marcescens. The Na(+) content of the cells was normally low and did not increase as the cells aged or when the cells were grown in media of high ionic strength. The transport of K(+) by resting cells suspended in hypertonic solution was studied by chemical and light-scattering techniques and was found to be more rapid in S. marcescens than in S. marinorubra. The slower rate of K(+) transport in S. marinorubra is probably related to the lower glycogen reserves found in resting cells of this microorganism. K(+) transport was found to have a pH optimum of 5.5 to 6.1 for S. marcescens, and the K(m) for K(+) was approximately 1.6 mm. Na(+) and Mg(2+) were not taken up by the cells, although the presence of Mg(2+) tended to decrease rates of K(+) uptake. Tris-(hydroxymethyl)aminomethane, routinely used for resuspending the cells, was apparently taken up by the cells at pH >7.     

Efflux systems in Serratia marcescens

A widespread bacterium Serratia marcescens (family Enterobacteriaceae) is an opportunistic pathogen and exhibits multiple drug resistance. Active removal of antibiotics and other antimicrobials from the cells by efflux systems is one of the mechanisms responsible for microbial resistance to these compounds. Among enterobacteria, efflux systems of Escherichia coli and Salmonella enterica ser. Typhimurium have been studied most extensively. Few efflux systems that belong to different families have been reported for S. marcescens. In this review, we analyzed available literature about S. marcescens efflux systems and carried out the comparative analysis of the genes encoding the RND type systems in different Serratia species and in other enterobacteria. Bioinformatical analysis of the S. marcescens genome allowed us to identify the previously unknown efflux systems based on their homology with the relevant E. coli genes. Identification of additional efflux systems in S. marcescens genome will promote our understanding of the physiology of these bacteria, will detect new molecular mechanisms of resistance, and will reveal their resistance potential.