Intracellular location of carotenoid pigments and some respiratory enzymes in Sarcina lutea

Effects of Light on Growth and Metabolism of Rhodococcus erythropolis

Rhodococcus erythropolis is resilient to various stressors. However, the response of R. erythropolis towards light has not been evaluated. In this study, R. erythropolis was exposed to different wavelengths of light. Compared to non-illuminated controls, carotenoid levels were significantly increased in white (standard warm white), green (510 nm) and blue light (470 nm) illuminated cultures. Notably, blue light (455, 425 nm) exhibited anti-microbial effects. Interestingly, cellular lipid composition shifted under light stress, increasing odd chain fatty acids (C15:0, C17:1) cultured under white (standard warm white) and green (510 nm) light. When exposed to blue light (470, 455, 425 nm), fatty acid profiles shifted to more saturated fatty acids (C16:1 to C16:0). Time-resolved proteomics analysis revealed several oxidative stress-related proteins to be upregulated under light illumination.

Optimizing the localization of astaxanthin enzymes for improved productivity

BACKGROUND

One important metabolic engineering strategy is to localize the enzymes close to their substrates for improved catalytic efficiency. However, localization configurations become more complex the greater the number of enzymes and substrates is involved. Indeed, optimizing synthetic pathways by localizing multiple enzymes remains a challenge. Terpenes are one of the most valuable and abundant natural product groups. Phytoene, lycopene and β-carotene serve as common intermediates for the synthesis of many carotenoids and derivative compounds, which are hydrophobic long-chain terpenoids, insoluble in water and usually accumulate in membrane compartments.

RESULTS

While β-ionone synthesis by β-carotene cleavage dioxygenase PhCCD1 and astaxanthin synthesis by β-carotene ketolase (CrtW) and β-carotene hydroxylase (CrtZ) differ in complexity (single and multiple step pathways), the productivity of both pathways benefited from controlling enzyme localization to the E. coli cell membrane via a GlpF protein fusion. Especially, the astaxanthin synthesis pathway comprises both CrtW and CrtZ, which perform four interchangeable reactions initiated from β-carotene. Up to four localization strategies of CrtW and CrtZ were exhaustively discussed in this work, and the optimal positioning strategy was achieved. CrtW and CrtZ were linked using a flexible linker and localized to the membrane via a GlpF protein fusion. Enzymes in the optimal localization configuration allowed a 215.4% astaxanthin production increase.

CONCLUSIONS

This work exploits a localization situation involving membrane-bound substrates, intermediates and multiple enzymes for the first time, and provides a workable positioning strategy to solve problems in similar circumstances.

Transporter-mediated biofuel secretion

Engineering microorganisms to produce biofuels is currently among the most promising strategies in renewable energy. However, harvesting these organisms for extracting biofuels is energy- and cost-intensive, limiting the commercial feasibility of large-scale production. Here, we demonstrate the use of a class of transport proteins of pharmacological interest to circumvent the need to harvest biomass during biofuel production. We show that membrane-embedded transporters, better known to efflux lipids and drugs, can be used to mediate the secretion of intracellularly synthesized model isoprenoid biofuel compounds to the extracellular milieu. Transporter-mediated biofuel secretion sustainably maintained an approximate three- to fivefold boost in biofuel production in our Escherichia coli test system. Because the transporters used in this study belong to the ubiquitous ATP-binding cassette protein family, we propose their use as "plug-and-play" biofuel-secreting systems in a variety of bacteria, cyanobacteria, diatoms, yeast, and algae used for biofuel production. This investigation showcases the potential of expressing desired membrane transport proteins in cell factories to achieve the export or import of substances of economic, environmental, or therapeutic importance.

Comparative study of lethal photosensitization of Sarcina lutea by 8-methoxypsoralen and by toluidine blue

Mathews, Micheline M. (Department of Bacteriology, University of California, Berkeley). Comparative study of lethal photosensitization of Sarcina lutea by 8-methoxypsoralen and by toluidine blue. J. Bacteriol. 85:322-328. 1963.-A comparative study has been made of the photo-killing of Sarcina lutea by 8-methoxypsoralen (8-MOP) and by toluidine blue. It has been found that photosensitization by 8-MOP differs from photosensitization by toluidine blue, in that it has a temperature coefficient of less than one, and that the presence of oxygen is not necessary for, and even is deleterious to, the photosensitization, the psoralen being destroyed by its presence. It has previously been shown that the presence of carotenoid pigments protects the cells of S. lutea from lethal photosensitization by toluidine blue; it was found that the presence of these pigments has no protective effect in photosensitization with 8-MOP. Studies on the lethal photosensitization of S. lutea with toluidine blue suggested that the primary sensitive site of the photokilling was the protein of the cell membrane, as manifested by the destruction of membrane enzyme activity and the regulation of permeability. It has been found that photokilling by 8-MOP has no effect on these functions. A study was made on the effect of photokilling by 8-MOP on the production of penicillin-resistant mutants as an indication of an alteration in the cellular deoxyribonucleic acid (DNA) by the psoralen. Psoralen photosensitization resulted in the development of many penicillin-resistant mutants. On the basis of the findings reported in this paper, it is suggested that photosensitization of S. lutea by 8-MOP does not reflect damage to cellular protein, as does toluidine blue, but rather damage to cellular DNA.

INHIBITORY ACTION OF PHAGE K ON STAPHYLOCOCCAL DEHYDROGENASES. II. ITS POSSIBLE RELATIONSHIP TO SENSITIZATION AND CELL LYSIS

Ralston, D. J. (University of California, Berkeley) and M. D. Perry. Inhibitory action of phage K on staphylococcal dehydrogenases. II. Its possible relationship to sensitization and cell lysis. J. Bacteriol. 86:740-748. 1963.-By measuring the reduction of the dye triphenyl tetrazolium chloride to the insoluble red formazan, an analysis was made of the inhibition by phage K of the dehydrogenase capacity of populations of Staphylococcus aureus K(1), to determine to what extent this might be associated with the ability of phage K to sensitize the cells-a reaction characterized by the conversion of the cell wall to susceptibility to lysis by the staphylococcal enzyme, virolysin. Increasing multiplicities of phage progressively increased the fractions of sensitized cells and also caused increasing inhibition of the dehydrogenase activity of the populations. The dehydrogenase activities of the sensitized fractions were compared with those of the nonsensitized fractions. Over a wide range of phage-bacterium ratios, the dehydrogenase activities of the sensitized fractions were found to be lower than those of the nonsensitized fractions. Microscopically, this was reflected by the appearance of large numbers of cells with a reduced amount of visible formazan granules. When lysin was added to the phage-treated cells, lysis occurred mainly from cell fractions which possessed little or no tetrazolium-reducing capacity. The data indicated that sensitization by phage was accompanied by a marked decrease in cellular dehydrogenase activity but was not associated with a complete inhibition of these enzymes. A comparison was made between the dehydrogenases of phage-sensitized cells and cells found to be "spontaneously" sensitive to virolysin, i.e., lysed by the enzyme without any prior exposure to phage. Like phage-sensitized cells, the spontaneously sensitized staphylococci possessed low dehydrogenase activity and lacked the capacity to support phage synthesis. In tests of a given cell preparation, the dehydrogenase levels of the phage-sensitized fractions were found to be close to, or even lower than, the level of the spontaneously sensitized fraction, suggesting that in S. aureus K(1) the sensitized state is associated in some manner with a reduction of the dehydrogenase activity to a critical level. There is as yet no evidence for any direct causal relationship between sensitization and dehydrogenase inhibition.

The photosensitivity of the malate oxidase system of a pigmented strain and a carotenoidless mutant of Sarcina lutea (Micrococcus luteus)

The effect of white light on the malate oxidase of Sarcina lutea (Micrococcus luteus) membranes has been examined using a carotenoid-containing and a carotenoidless mutant. At least three photosensitive sites have been detected. Two of these are associated with the malate dehydrogenase complex (malate-menaquinone reductase) and are unaffected by membrane carotenoid. A third site which has been detected beyond the dehydrogenase complex, is protected by carotenoid since it can only be demonstrated in carotenoidless systems. A repair mechanism has been found for one of the two sites in the dehydrogenase complex.

Mycobacterium

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Fractionation and characterization of the plasma and mesosome membrane of Listeria monocytogenes

Protoplasts of Listeria monocytogenes strain 42 were fractionated after control lysis on a Ficoll (a polysucrose) density gradient. Visually, five zones could be recognized in the gradient. The first one was composed of amorphous cytoplasmic solutes (fraction 1a) and a mixture of particles (fraction 1b). These were: (i) light particles that were lipase-sensitive and composed of six subunits and (ii) heavy particles, sensitive to ribonuclease and devoid of fine structure. The second zone consisted of tubules and vesicles still harboring cytoplasmic components (fraction 2), whereas the third zone contained only empty vesicles and protoplast ghosts (fraction 3). The material congregating into the fourth zone was morphologically identical to that of the third (fraction 3a). The fifth and heaviest zone contained a mixture of (i) particles without any substructure and (ii) partly lysed protoplasts (fraction 4). Fractions 1b and 4 were the richest in nucleic acids (ribonucleic acid, 11.4 and 9.4%, respectively; deoxyribonucleic acid, 5.1 and 4.8%, respectively), whereas fraction 1b had the highest protein contents (74.6%). Phospholipids were mainly found in fractions 2 and 3. Except for fraction 1, all materials contained significant amounts of protein-bound phosphorus. The main concentrations of four enzymes were: glucose-6-phosphate dehydrogenase (fraction 1a); adenosine triphosphatase and reduced nicotinamide adenine diphosphate oxidase (fraction 3); nitro blue tetrazolium chloride reductase (fraction 2). Fractionation of strain 42 after addition of (32)P during the mid-log phase of growth revealed that the radio-activity was mainly detected in fraction 1b, when growth in the presence of the marker was allowed for 10 min, and in fraction 2, when growth was allowed for 90 min. The vesicles of fraction 2, often tubular, are probably of mesosomal origin, whereas those of fraction 3, which are always spherical, represent, most likely, the bulk of the cell plasma membrane. Our data showed slight chemical differences between these two fractions, but the differences in enzymatic activities and lipid-phosphorus incorporation during long pulse experiments were most dramatic.

Ultrastructure of nonphotosynthetic carotenoid-containing bacteria

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LOCALIZATION OF CAROTENOID PIGMENT IN THE CYTOPLASMIC MEMBRANE OF XANTHOMONAS JUGLANDIS

Stephens, William L. (University of California, Davis), and Mortimer P. Starr . Localization of carotenoid pigment in the cytoplasmic membrane of Xanthomonas juglandis . J. Bacteriol. 86: 1070–1074. 1963.—The kinetics of release of carotenoid pigment from cells of Xanthomonas juglandis , disrupted by sonic or ballistic treatment, showed the pigment to be localized in the cell envelope. Cells subjected to ballistic disintegration released carotenoid at a rate identical to that of a membrane component (reduced nicotinamide adenine dinucleotide oxidase) and at a slightly higher rate than a wall component (hexosamine). Thus, the membrane portion of the cell envelope is the most probable locus of the unique carotenoid pigment of X. juglandis .

KINASES OF STREPTOCOCCUS FAECALIS I

Moore, L. Daneo (University of Pennsylvania, Philadelphia) and D. J. O'Kane . Kinases of Streptococcus faecalis . I. Enzyme localization. J. Bacteriol. 86: 766–772. 1963.—Cell-free extracts of Streptococcus faecalis 10C1 were found to contain a membrane-associated, particulate hexokinase with activity toward glucose, fructose, mannose, and, to a lesser extent, galactose, gluconate, and mannitol. In addition, the cell cytoplasm contained kinases specific for fructose, mannose, and galactose. No specific kinases were found for gluconate or mannitol, although in the presence of mannitol adenosine triphosphate was utilized by a cytoplasmic fraction. The possibility is discussed that the main pathways of gluconate and mannitol metabolism are oxidation followed by phosphorylation.

LOCATION OF PROTEINASE IN CELLS OF A SPECIES OF MICROCOCCUS

Micrococcus sp. (ATCC No. 407) grown in tryptone yeast extract broth produced proteinase active against casein. In broth containing 2.0% sodium chloride, about 90% of the proteinase was in the culture supernatant; in broth without added salt, about 66% was associated with the cells. When such cells were washed with 2% sodium chloride, about one-half the associated proteinase was released. Presumably this saline-extractable portion of the proteinase is loosely held at the ceil surface, possibly by ionic linkages. A further yield of proteinase could be obtained from saline-washed cells by treatments that ruptured the cells or altered the permeability of the cell membrane. This so-called bound proteinase became accessible to the substrate, but was not liberated into the suspending medium on lysozyme treatment of saline-washed cells. When lysozyme-treated cells were fractionated, the proteinase was found with the cytoplasmic membrane fraction. During sonic treatment of saline-washed cells, the bound. proteinase was released without appreciable disintegration of the cell envelope suggesting that it may not be an integral part of the cell membrane.