What is the reason behind production of large holes in 'Swiss Cheese'?

The production of large amount of $\displaystyle \mathrm{CO}_2$ by Propionibacterium sharmanii

The production of large amount of $\displaystyle \mathrm{CO}_2$ by Clostridium butylicum

The production of large amount of $\displaystyle \mathrm{CO}_2$ and $\displaystyle \mathrm{H}_2$ by lactic acid bacteria called Lactobacillus

The production of large amount of $\displaystyle \mathrm{CO}_2$ and $\displaystyle \mathrm{H}_2$ by Trichoderma polysporum