Fol ia Mierobiol. 19, 9 - -11 (1974)

The Influence of Tetrathionate Respiration on Catabolite Repression in Citrobacter M. I~EZBOVX and F. KAPRXLEK

Depa~?ment of Microbiology, Faculty of Science, Charles University, zOrague 2

Received May 31, 1973

ABSTRACT. . Anaerob ic reversa l o f ea tabol i te repregsion was pa r t i a l ly e l i m i n a t e d if t e t r a t h i o n a t e was ~edueed to t h iosu lpha te .

Many facultatively anaerobic bacteria reduce tetrathionate enzymically to thio- sulphate under anaerobic conditions (LeMinor and Pichinoty, 1963). Little is known about the physiological significance of this reduction. Some results (Stouthamer and Bettenhaussen, 1972; Kapr~lek, 1972) indicate that this activity may be a form of anaerobic respiration analogous to the reduction of nitrate to nitrite which is known to be coupled with oxidative phosphorylation (Hadjipetrou and Stouthamer, 1965; John and Whatley, 1970). In an attempt to compare tetrathionate respiration with nitrate respiration we used as a criterion the influence of both processes on catabolite repression. We started from the original finding of Cohn and Horibata (1959) that catabolite repression of ~-galaetosidase by glucose could be overcome by anaerobiosis, and from the fact (Dobrogosz, 1965) that this reversal of catabolite repression did not take place if nitrate reduction occurred anaerobically. The question was whether similar results would be found in the case of tetrathionate reduction.

M A T E R I A L S AND MET HODS

The differential rate of ~-galactosidase synthesis was measured in Citrobacter grow- ing at 30~ in a complex medium (Kaprs and Pichinoty, 1970) with glucose, fructose or galactose (2 g/litre) as energy source under four types of experimental conditions: aerobically, anaerobically, anaerobically with K2SaO~ (10 ~mol/ml) and anaerobically with KNOa (5 ~zmol/ml). A culture growing exponentially in the same medium under identical conditions served as inoculum. During exponential growth 0.001M (final concentration) methyl-~-D-thiogalactopyranoside was added as induc- tor. At suitable time intervals ~-galaetosidase activity was determined (Dobrogosz, 1965) in units of activity per ml culture (one unit hydrolyzes one nmol o-nitrophenyl- -D-galactopyranoside per rain) and plotted against biomass concentration (~g dry wt./ml).

RESULTS AND DISCUSSION

The results with galactose as energy source are presented in Fig. 1 and demon- strate the influence of different kinds of electron acceptors on ~-galactosidase syn- thesis. Under aerobic conditions the synthesis was more repressed than under anaer-

10

90

8O

U/ml

70

6O

5O

4O

30

2O

M. ~ E Z B O V k A N D F . K A P R . ~ L E K Vol. 19

,~ L 0 50 I00 150 200

,ug

F Ie . 1. Different ia l r a t e o f ~-ga lae tos idase s y n t h e s i s in Citrobacter growing on ga lac tose in t h e p resence o f dif- f e r en t exogenous e l ec t ron a c c e p t e r s . . , , Anae rob ica l l y w i t h o u t accep te r ; D , anae rob ica l ly w i t h K2S40~; Q , an - aerobica l ly w i th K N O s ; O , aerobical ly . U / m L e n z y m e un i t s pe r ml ; ~tg, g r o w t h in [zg d r y wt . /ml .

obic conditions with no external electron accepter. Anaerobic respiration of tetra- thionate as well as of ni trate leads to intermediary values. Similar results were found on fructose and glucose and are summarized in Table I. I t may be seen tha t anaer- obic respiration of te t ra thionate influences catabolite repression on all three sugars tested and in this respect resembles aerobic respiration and nitrate respiration.

These findings together with our previous results (Kapr~lek, 1972) indicate tha t

TABLE I. T h e effect o f d i f ferent exogenous e lec t ron accep te r s on t h e di f ferent ia l r a t e o f ~ -ga lac tos idaso s y n t h e s i s

Source o f ene rgy a n d e lec t rons

E x o g e n o u s accep te r

o f e lec t rons

Cu l t i va t i on cond i t ions

Dif ferent ia l r a t e o f e n z y m e s y n t h e s i s

( uni tslml ) / (~g/ml ) %

Galac tose

F ruc tose

Glucose

N o n e 1 1.68 -4- 0.05 I00.0 K2S406 1 1.22 ~ 0 .08 74.0 K N e e 1 1.16 -4- 0 .17 70.2 O3 z 0 .66 -4- 0 .02 35.7

None 1 1.53 :{: 0.02 100.O K2S406 1 0.60 4- 0.00 39.2 K N O 3 1 0.57 q- 0.24 37.2 02 ~ 0.26 ~ 0.02 16.9

None t 0.16 :k 0.03 100.0 K2S40e 1 0.12 q- 0.01 75.0 K N e e 1 0.07 -}- 0.02 44.3 02 2 0.03 • 0.00 18.8

I Anaerobic , s aerobic.

1974 TETRATHIONATE RESPIRATION 11

transfer of electrons to tetrathionate (as well as to nitrate) has the same qualitative, even though not quantitative, consequences for cell physiology as has the electron transfer to oxygen. Moreover, they support Dobrogosz's (1965) conclusion that the eatabolite repression mechanism is associated with some oxide-reduction processes in the cell.

R E F E R E N C E S

Co~ax M., ]-IoRIBATA K. : Physiology of the inhibition by glucose of the induced synthesis of the [3-galacto- side-enzyme system of E~cherichia coli. J . Bacteriol. 78, 624 (1959).

DOBROGOSZ W. J. : The influence of nitrate and nitrite reduction on catabolite repression in Escherichia coll. Biochim. Biophys . Acta 100, 553 {1965).

HADJIrETROU L. P., STOUT~AMER A. H.: Energy production during nitrate respiration by Aerobacter aerogenes. J . Gen. Mivrobiol. 38, 29 (1965).~

J o ~ P., W~ATLEY F. R.: Oxidative phosphorylation coupled to oxygen uptake and nitrate reduction in Micrococcus denitri f icans. Biochim. Biophys . Acta 216, 342 (1970).

KAPR~L~.K F. : The physiological role of tetrathionate respiration in growing Citrobacter. J . Gen. MicrobioL 71, 133 (1972)

KAPR.~LEK F., PICHINOTY F. : The effect of oxygen on te~rathionate reduetase activity and biosynthesis. J . Gen. MicrobioL 62, 95 (1970).

LE~I~OR L., PICH~OTY F.: Recherche de la t~trathionate-r~duetase chez les bact~ries Gram n6gatives anaerobies facultatives (Entvrobacteriaceae, Aeromonas et Pasteurclla). A n n . Ins t . Pasteu~ 104, 384 (1963).

STOUTHAMER A . H., BETTE~HAUSSEI~ C. : Influence of hydrogen accepters on growth and energy produc- tion of Proteu~ mirahil is . A nL van Leeuwenhoelc J . Microbiol. Serol. 38, 81 (1972).