Re: What are some bacteria in spoiled milk?

	I can give you some idea of the process, but I can't say I know 
what to do about it.  Milk has a lot of useful nutrients in solution or 
suspension.  These are good for people, but other living things like them, 
too.  Except for salt, almost everything in milk can be used by some 
microorganism.  The main nutrients are lactose (milk sugar), protein 
(various kinds), and butterfat, in 85 to 90% water.  
	The nutrient that is used fastest by bacteria is usually the 
lactose.  Several kinds of bacteria that always seem to be present and 
ready (especially the lactococci and lactobacilli) convert lactose to its 
component sugars (glucose and galactose) and then into lactic acid.  This 
is how milk sours, and the acid makes the principal milk protein (casein) 
precipitate, forming a curd.  So, if you taste the milk, you'll say it's 
sour; but if you look at it, you'll say it curdled.
	Curdling doesn't necessarily harm the protein.  The name "casein" 
more or less means "the protein of cheese," and it is these curds that form 
most of the solids of cheese, after the remaining liquid ("whey") is 
pressed out.  However, under other-than-cheesemaking conditions, other 
bacteria (e.g., pseudomonads) attack the protein and decompose it for their 
own use.  One name for protein decomposition is "putrefaction"; this 
probably goes with what you are smelling.  
	Milk fat (butterfat) can also be made rancid by microbial action, 
and that smells badly, too.  Additionally, the lactic acid that the 
bacteria made from lactose has lots of energy left in it.  If air is 
present, molds can use the lactic acid, decompose some of the protein, and 
probably attack the fat.
	The things I've described are what happens to milk in a bottle or 
carton — not necessarily after it soaks into a rug.  Bacteria need lots of 
water to grow well, so having the milk dry in the rug nap will gradually 
discourage them.  The partly dried residue is still fair game for the 
molds, but when the milk finally dries completely, things will pretty much 
stop happening until the spot gets wet again, with water, more milk, or (!) 
urine.  Then, the bacteria and molds that "went to sleep" in the dried on 
residue will perk up and do their thing until conditions get too dry again. 
 
	Even when the bacteria and molds are dormant because of dryness, 
the products they left behind (especially putrefied protein, and rancid 
butterfat) will continue to smell.  And because milk protein is very 
sticky, it is really hard to get the milk residue out of a carpet.  A 
professional carpet cleaner may be able to take care of spilled milk, but I 
don't know how.  All I know is there is no use crying over it.  Good luck!