The following organisms are close relatives of Penicillium chrysogenum.  There are numerous related fungi which I will not be mentioning, however.  The following fungi were chose based on popularity, morphological similarities (all belong to the Penicillium genus and contain a paintbrush-like conidiophore), as well as molecular similarities based on DNA similarities.  

Penicillium roquefortii

Penicillium roquefortii is one of the most well known relatives of P. chrysogenum.  It is used as a flavoring, antibiotic, and food source.  One of the most common uses of P. roquefortii is the flavoring of many varieties of blue cheese.  In fact, one type, Roquefort cheese, was named after the Roquefort Caves where it was first discovered, and as you have probably deduced, these caves were named after P. roquefortii.

Not all products of P. roquefortii are beneficial, however.  The fungus is also known to produce a tremor-inducing mycotoxin (a toxin produced by a fungus) which is called roquefortine.  It is included in a larger group of mycotoxins called Penitrem A.  It is characterized by severe muscle tremors, sweating, and loss of speech.  Most cases are seen in animals (usually dogs) which have ingested moldy foods.  Other cases have been seen in factory workers who have constant, direct contact with P. roquefortii.  

Penicillium fumiculosum

Like all other fungus, Penicillium fumiculosum is one of nature’s finest recyclers.  However, this fungus goes a step further; it is one of the best decomposers of almost all types of plastic fibers.  P. fumiculosum is also used as an antifungal antibiotic called Wortmannin.

Pencillium expansum

When you see an apple or pear covered in blue, fuzzy mold, you’re more than likely looking at the spores from Penicillium expansum. 

This fungus is characterized by giving fruit (usually apples) soft, rotted spots which are light brown.  Depending on how long the apple has been rotting, the coloration may vary from light brown to blue, yellow, or green.  If the contamination is from a different species of Penicillium, the rotting will more firm and take more time than if it were P. expansum.

P. expansum is also known to produce a cancer-causing mycotoxin called patulin.  Though levels of patulin are checked during fruit processing, it has produced harmful effects on people and animals.  On a less extreme level, patulin also makes fruit distasteful.  In order to combat this fungus as well as any unwanted mycotoxins, fruit producers use fungicides after harvest as well as a variety of other methods.