a) There are two contrasting explanations for how the large intestine gets colonized with what eventually becomes a stable community of bacteria.

a) There are two contrasting explanations for how the large intestine gets colonized with what eventually becomes a stable community of bacteria. According to the “deterministic” model, bacteria compete for available niches which are mostly determined by the host environment (genes, diet, defense mechanisms). According to the “neutral model,” bacterial colonization is largely a matter of chance according to which bacteria arrive first and their interactions with later would-be invaders.

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One test to decide between these models used lab organisms (mice and zebrafish) which can both be raised germ-free and later colonized with bacteria. When the distal gut bacteria of conventionally raised mice (conventional here means as opposed to germ-free) were transplanted to germ-free zebrafish, the gut microbiota initially resembled that of mice but quickly changed to a bacterial community more typical of that of conventionally raised zebrafish. Conversely, when zebrafish gut bacteria were transplanted into germ-free mice, the mice’s gut community soon shifted to a composition more typical of conventionally raised mice.

Which model does this experiment best support, the deterministic or the neutral? Explain your answer.