Can the communicating author remove some of the authors (4 out of 6) when submitting the second revision of a paper describing a database? Our paper was due submission for second revision at a BMC journal. The communicating author, as I understand is responsible for handling all the communications between all authors and the journal, while also making suitable arrangement to cover any open access charges. 

However, the communicating author in our case, without informing any author, removed 4 out of the total 6 authors while submitting the second revision. How should we deal with this? isn't it a academic fraud by the communicating author? Can't we, as students do anything to stop this?
This sounds like an unpleasant situation.

If this happened to me, I think my starting point would be to ensure I had copies of anything that might be useful as evidence. Then, I would write (formally) to the person concerned, asking for an explanation of why they thought it appropriate to remove you all from the author list. I think this has to be the first step: it is always possible that there is a rational explanation (although it's difficult to imagine what it might be). You might choose to copy the letter to the head of the relevant university department, and perhaps to the editor of the journal - particularly if the paper has not yet been published, and so can be put 'on hold' pending resolution of the authorship dispute. 

Of course, you will have to weigh up the benefits of asserting your rights to authorship against any potential cost arising from 'causing trouble'. You are completely within your rights to create a major fuss here, and your department should be entirely supportive. I think you should do something. However, there is a risk that some of the people involved will seek revenge, if they have any power over you (e.g. if you are still a student at the university). I am absolutely not condoning such behaviour - it is quite clearly bullying, and an abuse of power. However, it would be irresponsible to advocate taking action without encouraging you to also consider whether there are any potential adverse consequences.