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TOWARDS GENETIC MODIFICATION OF RUMEN BACTERIA FOR
IMPROVED PASTURE FIBRE DIGESTION

K.S. Gobius, G.P. Xue, and J.H. Aylward

CSIRO Division of Tropical Crops and Pastures, 306 Carmody Rd., St Lucia, Qld 4067

Improved microbial fibre digestion holds the potential to increase production in the Australian beef and sheep industries. The introduction of genes for improved fibre-degradation to rumen bacteria has been impeded by the lack of suitable genetic transformation systems. Genetic transformation of Butyrivibrio fibrisolvens is prerequisite for the expression of recombinant fibre-degrading genes within this group of rumen microorganisms. Escherichia coli/ B. fibrisolvens shuttle vectors have been described for B. fibrisolvens (1, 2, 3), however these vectors are limited in host range or utility. We have investigated the potential of the broad host range plasmid pUB110 to enable the expression of recombinant fibre-degrading genes in B. fibrisolvens strains.

MATERIALS AND METHODS

B. fibrisolvens strains were grown anaerobically in M2 medium (4) containing 0.5% w/v cellobiose. Plasmid DNA was isolated by alkaline lysis (5) from Bacillus subtilis or transformed B. fibrisolvens strains and then used to electroporate B. fibrisolvens (2).

RESULTS AND DISCUSSION

B. fibrisolvens strains isolated from the rumen of sheep (AR9, AR11, AR51), arctic reindeer (E14), cattle (H17c), white-tailed deer (OB156), water buffalo (LP1028), and goat (LP1309) were successfully transformed with the plasmid vector pUB110 and/or recombinant derivatives carrying hemicellulase (pUBxynA) or cellulase (pUBcelD) cDNAs isolated from the anaerobic rumen fungus Neocallimastix patriciarum (Table 1).

Table 1. B. fibrisolvens strains transformed with pUB110 and recombinant derivatives.

 

Plasmid Constructs

Strain(s)

pUB110

pUBxynA

pUBcelD

AR9, E14

+

   

AR11

+

+

 

AR51, H17c, LP1028, LP1309, OB156

+

+

+

The successful transformation of B. fibrisolvens strains with recombinant fibre-degrading genes will allow testing of the hypothesis that modified rumen bacteria may contribute to the improvement of fibre-digestion in livestock.

REFERENCES

1. Ware, C.E. et al. 1992. Current Microbiol. 24, 193-197.

2. Whitehead, T.R. 1992. Lett. Appl. Microbiol. 15, 186-189.

3. Beard, C.E. et al. 1995. Current Microbiol. 30, 105 - 109.

4. Hobson, P.N. 1969. In: Methods in Microbiology. (Eds J.R. Norris and D. W. Ribbons) (Academic Press: London). pp. 133-149.

5. Bron, S. 1990. In: Molecular Biological Methods for Bacillus. (Eds C.R. Harwood and S.M. Cutting) (Wiley and Sons: Chichester). pp. 140-141.

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