Gastrointestinal disease is a major cause of morbidity and mortality worldwide 
each year. Treatment of chronic inflammatory gastrointestinal conditions such as 
ulcerative colitis and Crohn's disease is difficult due to the ambiguity 
surrounding their precise aetiology. Infectious gastrointestinal diseases, such 
as various types of diarrheal disease are also becoming increasingly difficult 
to treat due to the increasing dissemination of antibiotic resistance among 
microorganisms and the emergence of the so-called 'superbugs'. Taking into 
consideration these problems, the need for novel therapeutics is essential. 
Although described for over a century probiotics have only been extensively 
researched in recent years. Their use in the treatment and prevention of 
disease, particularly gastrointestinal disease, has yielded many successful 
results, some of which we outline in this review. Although promising, many 
probiotics are hindered by inherent physiological and technological weaknesses 
and often the most clinically promising strains are unusable. Consequently we 
discuss various strategies whereby probiotics may be engineered to create 
designer probiotics. Such innovative approaches include; a receptor mimicry 
strategy to create probiotics that target specific pathogens and toxins, a 
patho-biotechnology approach using pathogen-derived genes to create more robust 
probiotic stains with increased host and processing-associated stress tolerance 
profiles and meta-biotechnology, whereby, functional metagenomics may be used to 
identify novel genes from diverse and vastly unexplored environments, such as 
the human gut, for use in biotechnology and medicine.