I believe you would be talking about the text by Ray Bradbury, "The One Who Waits." It begins in a well on Mars and the bacteria/alien takes over each human causing them to kill themselves then taking host of someone else.

I live in a well. I live like smoke in the well. Like vapor in a stone throat. I don't move. I don't do anything but wait. Overhead I see the cold stars of night and morning, and I see the sun. And sometimes I sing old songs of this world when it was young. How can I tell you what I am when I don't know? I cannot. I am simply waiting. I am mist and moonlight and memory. I am sad and I am old. Sometimes I fall like rain into the well. Spider webs are startled into forming where my rain falls fast, on the water surface. I wait in cool silence and there will be a day when I no longer wait.

Here is a link to the pdf of it. https://mrchrisattlc.weebly.com/uploads/2/3/4/8/23481786/the-one-who-waits_short_story.pdf

I believe you would be talking about the text by Ray Bradbury, "The One Who Waits." It begins in a well on Mars and the bacteria/alien takes over each human causing them to kill themselves then taking host of someone else.

I live in a well. I live like smoke in the well. Like vapor in a stone throat. I don't move. I don't do anything but wait. Overhead I see the cold stars of night and morning, and I see the sun. And sometimes I sing old songs of this world when it was young. How can I tell you what I am when I don't know? I cannot. I am simply waiting. I am mist and moonlight and memory. I am sad and I am old. Sometimes I fall like rain into the well. Spider webs are startled into forming where my rain falls fast, on the water surface. I wait in cool silence and there will be a day when I no longer wait.