Bacterial behaviour.
Posted: Fri Sep 18, 2020 2:35 am
Increasinhly I find myself more interested in the behaviour of micro-organisms than the splendour of their structure. It is difficult to imagine cognizance in such tiny bodies yet here I relate two recent phenomena.
Part of my microscopy involves a frequent return to certain creeks, with an eye to look for changes. It's a long project..
Some samples from the spring were reviewed at the time and then set aside. Sometimes I return the samples and sometimes if there is something of interest I keep it, replenishing it with water and sometimes nutrient. One spring sample had a species of 35 micron amoeba that I was interested in looking at further with higher resolution DF and or phase at 13 or 1400X.
I didn't get to it until recently. One thing I found was that the population of bacteria had swelled, with an increased proportion if them being gliding bacteria. There is lots of motility in the sample. My initial observation was with Bright M phase, which reveals small organisms as brilliant white on a grey background. After a period of viewing at 430X, I went back to 100X in order to orient myself better and noticed a bright white band across the slide. It resembled the milky way across the field. Going to a higher magnification revealed that a group of about 10 species of bacteria were concentrating in a 50 micron band, which went most of the way across the sample, for thousands of microns. The organisms ranged from 1/2 micron to 10 or so and I counted 9 individual species. I observed the anomaly for a while then returned it to it's jar. A day later , when observing a drop from the same sample, the same thing happened. After about 15 minutes, an approximately 50 micron concentrated band of bacteria develops. The third time I witnessed it, it described a complete circle about 4000 microns in diameter. Usually , it is a line though and it can be quite straight. Organisms will stray from the band out about 50 microns either way but usually return to the area of concentration. Every time I take a sample, the same thing happens and it seems to have organization.
Has anyone else experienced this kind of behaviour? It seems that it might be a response to light.
The high concentration of organisms creates a dense wall. The sample also has a high population of gliding bacteria, some of which move in an undulating fashion, almost a wave form. The undulation is quite consistent and seems to require a certain amplitude to drive the creature forward. While none if these larger 60 or so micron bacteria show any tendency to contribute to the wall, they do show a desire to pass through it, initially without success. They are persistent, though. This results in one of the most interesting behaviours I have witnessed through a microscope. The heavy concentration of bodies restricts the ability of the undulating bacteria to penetrate the wall, I am guessing due to a restriction in amplitude. They can however reverse and their response is to back out and try again and again, and each time they try to pass through the same area the body concentration restricts the undulation sufficiently that forward motion ceases, when they are about 1/2 way through. Here is where it gets interesting. The gliding bacteria, will back out yet again and change the angle of approach to the bacterial wall, therefore passing through a different portion. If that doesn't work, it does it again and eventually it finds a passage sufficiently open enough that it can pass through. I have witnessed this change of angle technique dozens of times.
This certanly shows something other than an automatic programmed response.
Part of my microscopy involves a frequent return to certain creeks, with an eye to look for changes. It's a long project..
Some samples from the spring were reviewed at the time and then set aside. Sometimes I return the samples and sometimes if there is something of interest I keep it, replenishing it with water and sometimes nutrient. One spring sample had a species of 35 micron amoeba that I was interested in looking at further with higher resolution DF and or phase at 13 or 1400X.
I didn't get to it until recently. One thing I found was that the population of bacteria had swelled, with an increased proportion if them being gliding bacteria. There is lots of motility in the sample. My initial observation was with Bright M phase, which reveals small organisms as brilliant white on a grey background. After a period of viewing at 430X, I went back to 100X in order to orient myself better and noticed a bright white band across the slide. It resembled the milky way across the field. Going to a higher magnification revealed that a group of about 10 species of bacteria were concentrating in a 50 micron band, which went most of the way across the sample, for thousands of microns. The organisms ranged from 1/2 micron to 10 or so and I counted 9 individual species. I observed the anomaly for a while then returned it to it's jar. A day later , when observing a drop from the same sample, the same thing happened. After about 15 minutes, an approximately 50 micron concentrated band of bacteria develops. The third time I witnessed it, it described a complete circle about 4000 microns in diameter. Usually , it is a line though and it can be quite straight. Organisms will stray from the band out about 50 microns either way but usually return to the area of concentration. Every time I take a sample, the same thing happens and it seems to have organization.
Has anyone else experienced this kind of behaviour? It seems that it might be a response to light.
The high concentration of organisms creates a dense wall. The sample also has a high population of gliding bacteria, some of which move in an undulating fashion, almost a wave form. The undulation is quite consistent and seems to require a certain amplitude to drive the creature forward. While none if these larger 60 or so micron bacteria show any tendency to contribute to the wall, they do show a desire to pass through it, initially without success. They are persistent, though. This results in one of the most interesting behaviours I have witnessed through a microscope. The heavy concentration of bodies restricts the ability of the undulating bacteria to penetrate the wall, I am guessing due to a restriction in amplitude. They can however reverse and their response is to back out and try again and again, and each time they try to pass through the same area the body concentration restricts the undulation sufficiently that forward motion ceases, when they are about 1/2 way through. Here is where it gets interesting. The gliding bacteria, will back out yet again and change the angle of approach to the bacterial wall, therefore passing through a different portion. If that doesn't work, it does it again and eventually it finds a passage sufficiently open enough that it can pass through. I have witnessed this change of angle technique dozens of times.
This certanly shows something other than an automatic programmed response.