Today we know more than _______that have been isolated from over_________of bacteria each of which recognize difference recognition sequences.

Answer

To solve the fill-in-the-blank question, we need to identify the specific numbers that fit into the statement provided. The statement is:

"Today we know more than _______ that have been isolated from over_________ of bacteria each of which recognize different recognition sequences."

### Step-by-Step Solution:

1. **Identify the Topic**: The question revolves around restriction endonucleases, which are enzymes that cleave DNA at specific recognition sequences.

2. **Determine the First Blank**: We need to find out how many restriction endonucleases are known. According to the information provided, we know more than 900 restriction endonucleases.

3. **Determine the Second Blank**: Next, we need to find out from how many strains of bacteria these restriction endonucleases have been isolated. The information indicates that they have been isolated from over 230 strains of bacteria.

4. **Fill in the Blanks**: Now we can fill in the blanks with the identified numbers:
- First Blank: 900
- Second Blank: 230

5. **Final Statement**: Combining the information, the complete statement reads:
"Today we know more than 900 restriction endonucleases that have been isolated from over 230 strains of bacteria each of which recognize different recognition sequences."

### Final Answer:
"Today we know more than **900** that have been isolated from over **230** of bacteria each of which recognize different recognition sequences."