rhodospirillum is a genus in the family rhodospirillaceae , a family of purple non - sulphur bacteria of the order rhodospirillales and the class alpha - proteobacteria . rhodospirillaceae are , among other characteristics , characterized by being phototrophic , and growing both aerobically and anaerobically , using light as an energy source . to that purpose , the bacteria contain chlorophyll b . within the genus rhodospirillum , three species are distinguished , e . g . rhodospirillum rubrum ( imhoff and trüper , 1992 ), rhodospirillum centenum and rhodospirillum photometricum . additionally , four species are not officially recognized , vz . rhodospirillum salexigens , rhodospirillum salinarum , rhodospirillum sodomense , and rhodospirillum tenue . in the genus phaeospirillum , another member of the family rhodospirillaceae , two species are included : phaeospirillum fulvum and phaeospirillum molischianum . ( for nomenclature see imhoff et al ( 1998 ); euzëby ( 2003 ); and reference 1 ). rhodospirillum rubrum is found , among others , in natural waters , in mud , and in sewage treatment plants . the bacterium is used in sewage purification , for biomass production of animal foodstuff ( for example as feed for poultry and fish ), and as a fertilizer . biomass of phototrophic bacteria is considered an excellent raw material for animal feed because of its high content of vitamins and amino acids . the use of rhodospirillum rubrum as animal feed has been practiced for some time ( imhoff and trüper , 1992 ). the present inventors , however , surprisingly found that r . rubrum may importantly contribute to the prevention of cardiovascular disease by lowering the cholesterol level in blood plasma and / or blood serum ( blood ). a cholesterol - lowering property is herein defined as the capability of a composition , a preparation , a food supplement or a foodstuff , when administered to the body of a subject in the appropriate manner , to lower the cholesterol level of the blood of said subject . methods for measuring the level of cholesterol in blood are known to the skilled person . a preparation of rhodospirillum spp . and / or phaeospirillum spp . is herein defined as an amount of cellular material of rhodospirillum spp . and / or phaeospirillum spp . which has been processed in some way . a preparation of rhodospirillum spp . and / or phaeospirillum spp . may , according to some embodiments of the present invention , comprise a cellular extract , or a component with cholesterol - lowering properties isolated from cells , or a concentrate of whole cells , or a concentrate of broken cell fragments . such a preparation may preferably comprise the membrane fraction . in addition , a preparation may , according to the invention , contain freeze - dried rhodospirillum spp . and / or phaeospirillum spp ., which cells are still largely alive and able to resume cell division under more favourable circumstances . a preparation according to the invention may very well consist of one species from the genus rhodospirillum , but mixtures of different rhodospirillum spp . such as rhodospirillum rubrum , rhodospirillum centenum , rhodospirillum tenue , rhodospirillum photometricum , rhodospirillum salexigens , rhodospirillum salinarum , and / or rhodospirillum sodomense , or mixtures of phaeospirillum spp ., such as phaeospirillum fulvum and phaeospirillum molischianum may also be used . combinations of rhodospirillum spp . and phaeospirillum spp . are also encompassed in the present invention . preferably , a preparation of rhodospirillum spp . and / or phaeospirillum spp . comprises rhodospirillum rubrum and / or phaeospirillum molischianum , still more preferably the type species rhodospirillum rubrum strain atcc 11170 ( strain dsm 467 ) or strain atcc 25903 and / or phaeospirillum molischianum strain dsm 120 . ( atcc , american type culture collection ; dsmz , deutsche sammlung von mikroorganismen und zellkulturen ). a preparation of rhodospirillum spp . and / or phaeospirillum spp ., in embodiments of the present invention , may well contain 20 - 100 % ( w / w ), preferably 40 - 100 % ( w / w ), even more preferably 60 - 100 % ( w / w ), and optimally 80 - 100 % ( w / w ) of cellular material from rhodospirillum spp . and / or phaeospirillum spp ., said cellular material preferably being the membrane fraction or live or freeze - dried whole cells . in addition , a preparation may contain other components , depending upon the way the selected preparation is to be prepared . for instance , a preparation may still contain water , or , in the case of a freeze - dried preparation , glycerol or sucrose . in a preferred embodiment , a freeze - dried preparation of rhodospirillum spp . and / or phaeospirillum spp . is mixed with filling materials such as microcrystalline cellulose ( mcc ) or mannitol , with a binder such as hydroxypropylcellulose ( hpc ), and / or lubricants , such as stearic acid and / or other excipients , and pelleted as a dry powder , or prepared for application in a different way . such a preparation of rhodospirillum spp . and / or phaeospirillum spp . is very suitable for use as a medicament or pharmaceutical preparation to lower plasma cholesterol levels , preferably in human plasma . the preparation may also contain living cells of rhodospirillum spp . and / or phaeospirillum spp ., or dead cells , or cell remnants , etc . alternative embodiments of a preparation according to the present invention are equally possible . for instance , a preparation can be supplied as a fluid preparation containing solid components suspended , dispersed or emulsified in a watery fluid . such a composition can be used directly as a preparation according to the invention , or be processed into a food supplement in an alternative embodiment . in the present invention a food supplement is defined as a formulation that may be consumed in addition to a normal diet and that contains components that do not occur in a normal diet , or that occur in low amounts or in insufficient amounts , while sufficient or increased consumption of these components is desired . preferably , a food supplement is composed such that it is suitable for human consumption . consequently , a food supplement as defined in the present invention should preferably have a texture , taste and smell , but also a nutritional value , that makes the supplement suitable for human consumption . in embodiments of the present invention a food supplement with cholesterol - lowering properties comprises a preparation of rhodospirillum spp . and / or phaeospirillum spp . a food supplement according to the invention may suitably contain from 0 . 1 to 99 . 9 % ( w / w ) of a preparation of rhodospirillum spp . preferably , a food supplement contains 10 % to 90 % ( w / w ), even more preferably 30 to 75 % ( w / w ), of a preparation of rhodospirillum spp and / or phaeospirillum spp . to make a food supplement comprising a preparation of rhodospirillum spp . and / or phaeospirillum spp . suitable for consumption , components may be added to improve , for instance , texture , taste or smell . consequently , a food supplement according to the invention may comprise ( additional ) sources of protein , carbohydrate and fat , and vitamins , minerals , electrolytes , trace elements , and other suitable components , so that the food supplement may itself be used as a nourishing food . as a source of protein each and every protein that is suitable for use in nutritional formulations , and mixtures of these , can be used in a food supplement according to the invention . this type of proteins encompasses for instance animal proteins such as whey proteins , whey protein concentrates , whey powder , egg protein , egg albumin , casein , or milk albumin , and plant proteins such as soy protein , soy meal , or proteins from soy milk . for choosing the source of proteins to be used , the biological value of a protein may constitute an important criterion . caseinate , including calcium caseinate , but also whey , milk albumin , egg albumin , and total egg proteins , for instance , are proteins with a very high biological value , because they contain a large proportion of essential amino acids . suitable carbohydrates to be used in a food supplement according to the invention might , for instance , be simple short - chain carbohydrates such as mono - and disaccharides , but also polysaccharides , or a combination of both . a carbohydrate may be selected because of its suitable organoleptic properties . a complex carbohydrate may suitably be used as a food fibre . a food supplement according to the invention may contain , in some embodiments combinations of both simple and complex carbohydrates . as fat all edible oils and fats can be used . vitamins and minerals may be added , in conformity with the rules of the regulatory health authorities , and may encompass all vitamins and minerals endorsed by the above authorities , for instance vitamin a , b1 , b2 , b12 , c , d , e , and k , and folic acid , niacin , panthotenic acid , and biotin . as minerals for instance iron , zinc , iodine , calcium , magnesium , chromium , and selenium may be added . electrolytes such as sodium , potassium , and chloride , and trace elements and other additives may also form part of a food supplement according to the invention . such components are , if present , preferably used in the recommended concentrations . additionally , a food supplement according to the invention may contain components improving its texture , colourings and flavourings , aromatic substances , spices , fillers , emulgators , stabilizing compounds , preservatives , antioxidants , fibres , and other supplements such as amino acids , choline , lecithin , fatty acids , etc . the choice of such components will depend upon formulation , design , and preferences . the amounts of such components that can be added are known to the skilled person , while the choice of the amounts to be added may be guided by considering the recommended daily amounts ( rda ) for children and adults . emulsifiers may be added to stabilize the final product . examples of acceptable emulsifiers are lecithin ( e . g ., soy or egg ), and / or mono - and di - glycerides . as stabilizers , carobe , guar or carrageenan may , for instance , be used . preservatives may be added to increase the shelf life of the product . preferably , preservatives such as sodium sorbate , potassium sorbate , potassium benzoate , sodium benzoate , or calcium disodium edta are used . in addition to the carbohydrates mentioned above , natural or synthetic sweeteners , such as saccharides , cyclamates , aspartamine , acesulphame potassium , and / or sorbitol , may be added to the food supplement . the amounts of food supplement to be consumed can vary in size , and are not necessarily restricted to the dosages mentioned in the dosages advised . the term “ food supplement ” is not meant to be restricted to a specified weight , or to a specified dose of the food supplement . the composition of a food supplement according to the invention can in principle take any form that is suitable for human or animal consumption . in a preferred embodiment , the supplement is a dry powder that is suitable to be suspended , dispersed or emulsified in a watery fluid such as coffee , tea , broth , or fruit juice . to that end , the powder may be supplied in a dispenser . in an alternative preferred embodiment , the supplement is formulated , starting from dry powder , as a tablet . to this end , the composition of a food supplement according to the invention can suitably be supplied with fillers such as microcrystalline cellulose ( mcc ) and mannitol , binders such as hydroxypropylcellulose ( hpc ), lubricants such as stearic acid , and other excipients . a food supplement according to the invention may also be supplied as a fluid , in which the solid components have been suspended , dispersed or emulsified . such a composition may be directly mixed into a foodstuff , or can for instance be extruded and formatted into granules or other forms . in an alternative embodiment , a food supplement may be formulated in a solid form , such as a bar , a biscuit , or a roll . a food supplement is preferably formulated for oral consumption , possibly in combination with an acceptable carrier such as a capsule , a tablet , a water - miscible powder , or another form acceptable for administration , but may also be processed into a foodstuff . other aspects of the present invention concern ways of producing a preparation , a food supplement , or a foodstuff according to the invention . a method for the production of a preparation according to the invention may well involve the steps necessary for culturing cells of one or more rhodospirillum spp . and / or phaeospirillum spp ., to harvest the said culture , and to process the cells of the said culture into a preparation . details of such methods are , among others , described in the examples mentioned below . the skilled person will understand that various alternative methods can be used . during the culturing of cells of rhodospirillum spp . and / or phaeospirillum spp . anaerobic and phototrophic conditions are applied . as a carbon source , various organic nutrients can be used . very suitable culture media and growth conditions for cells of rhodospirillum spp . and / or phaeospirillum spp . are for example “ segers and verstraete medium ” ( segers and verstraete , 1983 ), using lactic acid ( about 2 . 7 gram / l ) as a carbon source , at a ph of about 6 . 8 - 6 . 9 , and at a temperature of 25 - 37 ° c ., preferably adapted to the specific requirements of the micro - organism involved , at constant light intensity from for instance strip lighting ( light intensity 300 μm quanta · m − 2 · s − 1 ) and anaerobically . other media suitable for culturing rhodospirillum spp . and / or phaeospirillum spp . are for example “ modified rhodospirillaceae medium ” ( dsmz medium # 27 , dmsz gmbh , braunschweig , germany ), or cens medium ( dsmz medium # 748 ). the cells are suitable to be cultured to a density of 0 . 01 - 50 mg / ml , preferably 1 - 5 mg wet weight / ml . cells may equally be grown anaerobically at 30 ° c . in 1 liter flasks containing a medium constituted out of 3 . 1 ml / 160 % dl - lactate solution , 3 g / l bacteriological peptone and 3 g / l yeast extract in tap water , the ph of the medium being 6 . 8 , and illuminated with an average photon radiation strength of 50 μm quanta · m − 2 · s − 1 , using 3 tungsten lamps of 40 w . after 3 days of growth , the optical density at 660 nm amounted 3 . 5 ( 1 . 2 g / kg dry weight ). once the cells have reached a suitable cell density , they can be processed into a preparation according to the invention using separation from the growth medium or harvesting by , for instance , centrifugation or filtration . the concentrated cell mass can then be used , either directly or after further processing , as a preparation according to the invention . further steps in the processing of cell material of rhodospirillum spp . and / or phaeospirillum spp . to obtain a usable preparation could involve , for example , a washing step , but might also involve further processing of the cells by extraction , or freeze - drying . a further step in the processing of cell material of rhodospirillum spp . and / or phaeospirillum spp . to obtain a usable preparation could involve the sonication of cells , followed by the separation of membranous material from cytoplasmatic material by centrifugation , followed by a further washing and recentrifugation step . a food supplement according to the invention may suitably be used to reduce intestinal cholesterol absorption , thus reducing the cholesterol level of blood plasma . another embodiment of the invention involves the application of a food supplement in a foodstuff with cholesterol - lowering properties . a method to prepare a cholesterol - lowering foodstuff involves the production of a foodstuff incorporating a food supplement . such a method might involve a step in which a foodstuff is first prepared in the normal way , followed by the addition of a preparation of rhodospirillum spp . and / or phaeospirillum spp . to the prepared foodstuff . also , it is possible to add a preparation of rhodospirillum spp . and / or phaeospirillum spp . to the foodstuff during its production . a foodstuff with cholesterol - lowering properties according to the invention contains characteristically 0 . 1 to 20 % ( w / w ), preferably 1 to 10 % ( w / w ), of the food supplement described above . the present invention involves finally a preparation of rhodospirillum spp . and / or phaeospirillum spp . to be used in a medicament to lower the cholesterol level of blood plasma . preferably , such a preparation should involve the species rhodospirillum rubrum and / or phaeospirillum molischianum . the invention will now be illustrated by the following examples , which should not be interpreted as limiting the present invention in any way . r . rubrum strain atcc 25903 was used for the production of the biomass used in the experiments . freeze - dried cells were rehydrated in medium r8ah ( atcc medium 550 ), and cultured in “ segers and verstraete medium ” ( see above ), using lactic acid ( 2 . 7 g / l ) as a carbon source , at ph 6 . 9 ± 0 . 1 . the final culture of the biomass used in the experiments took place in 20 liter - bioreactors , in the same culture medium , at 30 ± 1 ° c ., ph 6 . 8 ± 0 . 1 , and at constant light intensity ( strip light ; 300 μm quanta · m − 2 · s − 1 ), under anaerobic conditions . after five days of culture , the biomass ( 3 . 4 gram wet weight / l ) was harvested by continuous centrifugation , stored at − 40 ° c ., and freeze - dried . to examine the effect of culture conditions on the effectiveness of lowering the cholesterol level , r . rubrum atcc 25903 was also grown anaerobically at 30 ° c . in 1 liter flasks containing a medium constituted out of 3 . 1 ml / 160 % dl - lactate solution , 3 g / l bacteriological peptone and 3 g / l yeast extract in tap water . the ph of the medium was 6 . 8 . the flask were incubated in an incubator ( new brunschwick scientific , model g 25 ) on a magnetic stirrer ( variomag multipoint hp15 ). the flasks were illuminated with an average photon radiation strength of 50 μm quanta · m − 2 · s − 1 , using 3 tungsten lamps of 40 w . after 3 days of growth , the optical density at 660 nm amounted 3 . 5 ( 1 . 2 g / kg dry weight ) and cells were harvested by centrifugation at 6500 g , washed with demineralized water and freeze dried ( virtis freezemobile 24 ). r . rubrum cultured in this way produced the same effect on plasma cholesterol levels as did r . rubrum cells cultured as described in example 1 , which were used in most examples . another r . rubrum strain , dsm 467 , was grown anaerobically at 25 ° c . in the same way in the same medium as described for example 2 . cells were harvested after 3 days of growth at an optical density at 660 nm of 4 . 5 ( dry weight 1 . 4 g / kg ) and dried as described for example 2 . strain dsm 467 produced the same effect on plasma cholesterol levels as did strain atcc 25903 , which was used in most examples . another photosynthetic bacterium , phaeospirillum molischianum dsm 120 , was grown in 1 liter flasks with atcc 550 medium at 25 ° c . under anaerobic conditions as described for example 2 . cells were harvested after 3 days of growth at an optical density at 660 nm of 4 . 0 ( dry weight 1 . 2 g / kg ) and dried as described for example 2 . male wistar rats were fed a semi - synthetic rat chow , meeting nutritional requirements ( as defined in reference 9 ) ( hope farms , woerden , the netherlands ). one group of eight rats was given this basic chow . a second group of eight rats was given the same chow , but now containing in addition 10 % ( w / w ) of freeze - dried r . rubrum ( in exchange for sucrose ). both groups consumed approximately the same amount of food ( 31 ± 7 gram / day ), and showed the same increase in body weight over time . after eight weeks , all clinical chemistry - parameters measured ( plasma glucose , uric acid , urea , creatinine , got , gpt , haematocrit , and haemoglobin , and urinary glucose and protein ) were similar in both groups , except plasma cholesterol and plasma triglycerides . plasma cholesterol was significantly lower in the group fed the r . rubrum - containing diet ( 1 . 2 ± 0 . 1 mmol / l vs . 1 . 6 ± 0 . 1 mmol / l ; t - test , p & lt ; 0 . 0001 ), as were plasma triglycerides ( 0 . 5 ± 0 . 1 mmol / l vs . 1 . 4 ± 0 . 6 mmol / l ; p & lt ; 0 . 001 ) ( fig1 ). separation of the plasma lipoproteins by fast - protein - liquid chromatography ( fplc , åkta system of pharmacia - amersham ) showed that the decrease in cholesterol and triglycerides was due to a decrease of the plasma ldl fraction , while the hdl fraction remained unchanged in the r . rubrum - fed animals ( fig2 ). the r . rubrum - induced decrease in plasma cholesterol was thus specifically due to a decrease in ldl - cholesterol . methods used for measuring cholesterol and triglycerides , and for separating lipoproteins by fplc have been described by van vlijmen et al ( 1996 ) and post et al ( 2000 ). ten c57black / 6 mice were fed a normal semi - synthetic mouse chow for seven days . five mice were subsequently given the same chow for another seven days , while the remaining five mice were given for seven days the same mouse chow , but now containing 10 % ( w / w ) of r . rubrum . food intake was not significantly different between groups , and averaged 2 . 6 - 2 . 8 gram / mouse · day . after seven days , the plasma cholesterol level was 1 . 52 ± 0 . 07 mmol / l in the r . rubrum - fed mice , significantly lower than the plasma cholesterol level in the control group ( 1 . 86 ± 0 . 15 mmol / l ; t - test , p = 0 . 003 ) ( fig3 ). plasma triglyceride levels were unchanged . effect of r . rubrum in mice fed a “ western - type ” diet ten c57black / 6 mice were fed for three weeks a semi - synthetic diet , the so - called “ western - type ” diet , a diet containing 15 % ( w / w ) fat , and 0 . 25 % ( w / w ) cholesterol ( nishina et al , 1990 ). subsequently , five mice were fed the same diet for seven days , while another five mice were fed the same diet but containing in addition 10 % ( w / w ) r . rubrum ( some cholesterol was also added to this diet to keep its cholesterol content at 0 . 25 %). after these seven days , the cholesterol level in the control group was 3 . 07 ± 0 . 18 mmol / l , while in the group fed the diet containing r . rubrum the cholesterol level was 2 . 26 ± 0 . 21 mmol / l ( t - test , p = 0 . 0003 ) ( fig4 ). plasma triglycerides were not decreased . separation of the lipoproteins by fplc , showed that the ldl - cholesterol had practically disappeared from the plasma of mice fed the western - type diet containing r . rubrum , while the hdl - cholesterol showed no inter - group difference ( fig5 ). effect of r . rubrum in transgenic apoe * 3leiden mice fed a “ western - type ” diet in this experiment mice were used in which the human gene for the so - called leiden mutation of apolipoprotein e3 ( apoe * 3leiden ) had been incorporated by transgenesis . because of this transgenic change , these so - called apoe * leiden mice have a humanized lipoprotein profile , and are extremely suitable for studying the effect of compounds on lipoprotein metabolism ( van vlijmen et al , 1996 ; 1998 ). the study design was as follows : groups of mice were fed for 5 weeks “ western - type ” diet ( see above ) containing 0 . 25 % ( w / w ) cholesterol . this diet increased their plasma cholesterol level to 13 - 14 mmol / l . subsequently , the mice were randomized , on the basis of their plasma cholesterol level , into groups of six mice each . these groups were given the same diet , but containing in addition 0 , 0 . 625 , 1 . 25 , 2 . 5 , 5 or 10 % ( w / w ) freeze - dried r . rubrum . the cholesterol content of the diet was kept at 0 . 25 % by adding cholesterol as required . during the experiment , body weight and food intake were monitored . after the dietary change , blood was taken weekly to determine plasma cholesterol and triglyceride levels . also , the plasma lipoprotein pattern was determined groupwise in pooled samples by fplc . in addition , faeces were collected weekly on a group basis . after three weeks , vldl secretion was measured in the groups fed 0 % and 10 % r . rubrum ( terminal experiment ). the group fed 0 . 625 % r . rubrum was then changed to a diet containing 0 % r . rubrum , the group fed 2 . 5 % r . rubrum to 5 % r . rubrum , and the group fed 5 % r . rubrum to 10 % r . rubrum , to replace the two groups sacrificed . after another week , blood was again sampled from the four remaining groups . the results can be summarized as follows : the plasma cholesterol level was significantly reduced in the groups fed 5 % or 10 % r . rubrum cholesterol lowering was already very significant after one week in the 10 % r . rubrum group ( p & lt ; 0 . 0001 ), and after two weeks also in the 5 % r . rubrum group ( p & lt ; 0 . 001 ), and remained so for the three - week period ( fig6 ) this lower cholesterol level was due to a lowering of cholesterol in the vldl and ldl fractions , while the amount of cholesterol in the hdl fractions did not change ( fig7 ) to decide whether the cholesterol lowering was due to inhibition of cholesterol synthesis , the plasma concentration of lathosterol , a side product of the cholesterol synthesis pathway , was measured ( kempen et al , 1988 ). the plasma lathosterol level was not significantly different between the groups fed 0 , 5 or 10 % r . rubrum ; while , as mentioned above , the plasma cholesterol level was significantly lower in the 5 % and 10 % groups ( fig8 ). the ratio of plasma lathosterol to plasma cholesterol even increased significantly in the mice fed r . rubrum ( anova & lt ; p & lt ; 0 . 026 ). since the ( relative ) lathosterol concentration is a good reflection of the rate of cholesterol synthesis ( kempen et al , 1988 ), it can be concluded that the lowering of plasma cholesterol in the 5 % and 10 % r . rubrum - fed groups was not due to a decreased rate of cholesterol synthesis . the plasma levels of camposterol and β - sitosterol , two sterols that occur only in plants and can thus only be present in plasma after uptake from the intestines , decreased significantly in the groups fed either 5 % or 10 % r . rubrum ( fig9 ). the ratio of the plasma concentration of β - sitosterol to cholesterol did not change significantly ( anova , p = 0 . 26 ), however ; neither did the ratio of plasma camposterol to cholesterol . ( anova , p = 0 . 98 ). since the plasma concentration of cholesterol is determined by its rate of synthesis and its rate of absorption from the intestines , the fact that these ratios remained similar ( camposterol , β - sitosterol ; compare miettinen et al , 1990 ) or increased ( lathosterol ) demonstrates that the decrease in the plasma cholesterol concentration cannot be due to a decrease in cholesterol synthesis , but must rather be ascribed to an decreased absorption of sterols from the intestinal lumen . the synthesis of vldl by the liver ( measured as described by post et al , 2000 ) was not significantly different in the group fed 10 % r . rubrum , relative to the control group ( fig1 a , b ). although , after the injection of triton wr1339 , plasma triglyceride concentrations increased more rapidly in the group fed 10 % r . rubrum than in the control group ( fig1 a ), this should be ascribed to the higher amount of triglycerides in the vldl fraction of r . rubrum - fed mice ( fig1 b ), rather than to an increase in the secretion of vldl particles by the liver . the faecal excretion of neutral sterols ( especially cholesterol ) increased in the mice treated with r . rubrum ( fig1 ), while the faecal excretion of bile acids also increased slightly ( fig1 ). consequently , the faecal excretion of all sterols jointly ( neutral sterols plus bile acids ) increased ( fig1 ) ( see also text tables 1a and b ). effect of a membrane fraction of rhodospirillum rubrum on plasma cholesterol level in apoe * 3leiden mice five gram of freeze - dried r . rubrum was suspended in 25 ml of water , and sonicated in a branson sonifier b - 12 for one minute at full strength . the sonicate was then centrifuged at 21 , 000 rpm , and the supernatant and pellet were separated . the pellet was resuspended and recentrifuged . pellet and supernatant were separately mixed into the w - diet ( described above ) containing 0 . 25 % cholesterol to 10 % ( w / w ), assuming both pellet and supernatant to be equivalent to 5 gram of freeze - dried r . rubrum ( i . e ., the starting material ). groups of six apoe3 * leiden mice were fed diet w , or the diet w but also containing the pellet ( membraneous ) material , or the diet w but also containing the cytoplasmic material , for two weeks . at week 2 , plasma cholesterol was 15 . 7 ± 1 . 6 mmol / l in the mice fed the control diet w , in the mice fed the diet w also containing the cytoplasmic material , plasma cholesterol was 14 . 4 ± 2 . 1 mmol / l , while in the mice fed the diet w also containing the membraneous material , the plasma cholesterol was 6 . 7 ± 0 . 9 mmol / l , a significant reduction of 57 % relative to the control group ( t - test ; p & lt ; 0 . 001 ). effect of phaeospirillum molischianum on plasma cholesterol level in apoe * 3leiden mice eleven apoe * 3leiden mice were fed the “ western - type ” diet ( see above ) containing 0 . 25 % ( w / w ) cholesterol . this diet increased their plasma cholesterol level to 9 ± 3 mmol / l . subsequently , the mice were randomized , on the basis of their plasma cholesterol level , into groups of six mice each . the two groups were given the same diet , but containing in addition 0 or 10 % ( w / w ) freeze - dried phaeospirillum molischianum , as described above for r . rubrum . after ten days of feeding , plasma cholesterol averaged 10 ± 4 mmol / l in the group not given p . molischianum ( paired t - test : not significant ), and 5 ± 2 mmol / l in the group given 10 % p . molischianum in the feed ( paired t - test : p & lt ; 0 . 05 ). these experiments show that adding 5 % ( w / w ) or 10 % ( w / w ) of r . rubrum to a “ western - type ” diet reduces , in apoe * 3leiden mice , plasma cholesterol levels significantly . this decrease 1 . can fully be ascribed to a decrease of cholesterol carried in ( pro - atherogenic ) vldl and ldl particles , while ( anti - atherogenic ) hdl cholesterol remains unchanged ; 2 . is not caused by a decrease in cholesterol synthesis , since plasma lathosterol levels do not change , while the synthesis / secretion of vldl by the liver is also unchanged ; 3 . is not due to an increased excretion of bile acids , which is only slightly increased ; but 4 . is therefore most likely due to a decreased absorption of sterols from the intestines , as reflected by the increased excretion of cholesterol in the faeces ( see text table 1a ), and the decrease in plasma camposterol and β - sitosterol concentrations . 5 . is caused by membraneous cellular material , not by soluble cytoplasmatic cellular material . the cholesterol - lowering effect is caused by r . rubrum cultured under different conditions , is caused by at least two different strains of r . rubrum ( atcc 25903 and dsm 467 ), and is also caused by a related species , p . mnolischianum . all data are expressed as μmoles per 100 gram mouse per day 1 . deutsche sammlung von mikroorganismen und zellkulturen gmbh . bacterial nomenclature up - to - date . accessed dec . 6 , 2003 . www . dsmz . de / bactnom / bactname . htm . 2 . euzéby j p . list of bacterial names with standing in nomenclature . accessed dec . 6 , 2003 . www . bacterio . cict . fr / qr / rhodospirillum . html and www . bacterio . cict . fr / qr / phaeospirillum . html . 3 . hassel c a . animal models : new cholesterol raising and lowering nutrients . curr opin lipidol 1998 ; 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the present invention relates to cholesterol - lowering preparations , in particular to a bacterial preparation for use as a medicament for lowering of the blood cholesterol level . the present invention provides inter alia a preparation of rhodospirillum spp . and / or phaeospirillum with cholesterol - lowering effects , food supplements and foodstuffs comprising said preparation and methods for the preparation and use thereof .