SLIME CITY
This is an interesting term, said to be coined by Coghlan in 1996, first hinted at by Costerton & Associates (Montana State University, Bozeman) in 1992 when they focused on biofilms with confocal scanning laser microscopy. Without going into detail, suffice it to say that the city is an interactive, cooperative (I hold to Costertons' view) of different bacteria and protozoans akin to an organ of a multi organ entity, like plants and animals, within a walled enclosure all working together for mutual benefit. The EPS "threads" (like thick egg white) and the watery slime akin to watery egg white is the "house" that binds them together. Figure C (New Scientist, Aug/1996) illustrates the concept of "slime city" whose height is only limited by the LL and available nutrients.
BACTERIAL BLOOMS
Biofilms form by colonization by different bacteria thus the species with the largest population of initial cells will dominate, for a while. Then we have colonization by those who eat the most or the fastest or the longest cell, largest cell or with fast growth characteristics. It is obvious that eventually the population within a given area of a biofilm will reach a stage that something will happen, either massive die off (unlikely) or a "bloom". Not unlike what happens in all major cities. As the population exceeds the available jobs people move out. This bloom can be due to erosion, sloughing, biological or chemical. Erosion is a "normal" process, due to rapid growth of the biofilm mass, that leads to a shearing as the biofilm extends into the dynamic water above the LL. Sloughing is a rapid break away of large biofilm material that occurs for many reasons, one of which may be the formation of gas bubbles that weaken the substructure. The biological mode can involve the release of enzymes, surfactants or whatever by neighboring cells that can cause the whole structure to collapse. Similar to a prison breakout. The chemical mode can involve the removal of binding forces within the structure, cation exchange, pH changes for whatever reason and changes in ionic strength. It has been alluded that SCALE in piping is a contributing factor in LB proliferation.
However, in view of present biofilm knowledge that position can be seen as overly simplistic and a "grasping at straws". If one is referring to RUST BARNACLES in steel pipe, that's a different issue. Scale in PHW loops can be eliminated by installing a dual resin tank water softener in the cold potable makeup line, although this will not stop some scale from forming after the faucet valves no one involved in Legionella research would even hint that LD could thus be addressed. If one is addressing the salt film that builds up in exposed piping after use, that is a different issue altogether, however certainly not of significance within the context of the total picture if the water is not a recontamination source.
PROTECTION OFFERED
It is obvious that we have placed a formidable task before any -cide, oxidizing (Halogens, Ozone, Peroxide, Permanganate) or non-oxidizing (quats, etc...). For any halogen (chlorine) to be efficacious it must first meet the system organic demand, the outer watery slime. Then it must have a means to infiltrate the nonmoving LL BEFORE it can reach the inhabitants within not to mention those within the crevices of the system metal. As for non-oxidizing -cides, if it cannot penetrate the slime proper, it cannot effect a kill. This is WHY lab tests of various cides using Petrie Dish grown cells are doomed to failure, it does not represent the microbial world. To infer that WONDERCIDE is affective on real world Legionella based on flask tests of planktonic (free swimming) lab grown organisms is dangerous, misleading and not in the best interest of the client with a potential for catastrophe for the ignorant. As for heavy metal attack, Copper/Silver technology for potable supplies and Organo-Tin, copper, for open circulating systems the EPS has the ability to tie up heavy metals, thereby protecting the inhabitants within. This is WHY EPS is useful in sewage treatment plants. The slime extracts the heavy metals it will do so in black, nasty, sewage water, potable water and within a PHW loop.
METALLOTHIONEIN (MT)
An interesting group of cell constituents that serve to tie up, extract, remove heavy metals before they can have an adverse effect on the cell proper. All cells have the basic MT manufacturing constituents, it is a means for the cell to protect itself, i.e. survival of the fittest after millions of years existence, against heavy metal exposure. When we use a heavy metal to affect a kill, all that we have succeeded in doing is to kill those cells within a species with low MT generating capacity that were prone to that dosage, leaving those with higher capacity for MT production thus "selecting" for that specific trait. Eventually we will produce a bacterial population (LB?) that is "immune" to the dosage of that metal. The failures of Cu/Ag ionization systems could well be the tip of the ice berg. It should be noted that some bacteria have the ability to transfer that "immune trait" to other bacterial cells. Also, keep in mind that ALL cells possess this ability, thus in using a heavy metal approach ALL the cells will be busy neutralizing the metals and conferring the ability to other cells.
(Part II next week)
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Respectfully,
Frank Rosa
"Plumbers Protect The Health Of The World."
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