A previous paper (Eaton, 1934) described variants of the pneumococcus characterized by a tendency to undergo rapid spontaneous lysis under certain cultural conditions at 370C. These variants were produced by daughter-colony dissociation of smooth pneumococcus strains on blood agar at 250C. A further investigation of this method of dissociation revealed that a second and independent type of vari...

Previously established radiometric techniques were used to assess the effectiveness of combined antimicrobial drug-inhibitory drug (drug-inhibitor) treatment on two clinical isolates of the Mycobacterium avium complex representing three colony variants: smooth opaque (dome) (SmO), smooth transparent (SmT), and rough (Rg). All variants were identified as members of the M. avium complex; however,...

UNLABELLED Diverse colony morphologies are a hallmark of Burkholderia pseudomallei recovered from infected patients. We observed that stresses that inhibit aerobic respiration shifted populations of B. pseudomallei from the canonical white colony morphotype toward two distinct, reversible, yet relatively stable yellow colony variants (YA and YB). As accumulating evidence supports the importance...

A major distinction in the social organization of ant societies is the number of reproductive queens that reside in a single colony. The fire ant Solenopsis invicta exists in two distinct social forms, one with colonies headed by a single reproductive queen and the other containing several to hundreds of egg-laying queens. This variation in social organization has been shown to be associated wi...

Colony morphology has been used as an important identification and characterization criterion in bacteriology for many decades. However, the molecular mechanisms underlying the appearance of different colony types have been given little attention. The synthesis of O antigen is defunct in Escherichia coli K-12, and colonies should accordingly only appear to be rough. However, previous reports ha...

The B16 melanoma-derived low lung-colonizing variant B16-F1 and the high lung-colonizing variant B16-F10 retained their differential lung-colonizing abilities throughout at least 35 serial s.c. transplant generations. The majority of the cells originating from solid B16-F1 tumors had a higher density than did cells originating from solid B16-F10 tumors. Cell suspensions of unselected solid B16 ...

A continuous-culture system was developed to study changes in the structure of Staphylococcus epidermidis populations exposed to subminimum inhibitory concentrations of erythromycin. Continuous-culture experiments were carried out in a dextrose-free, tryptic soy broth medium supplemented with lactic acid and sodium lactate (MTSB-D). The multiresistant (penicillin-, tetracycline-, and erythromyc...

Production of extracellular polysaccharide by the marine bacterium Pseudomonas atlantica is a variable trait. Strains that produce extracellular polysaccharide (EPS(+)) have a mucoid colony phenotype, but during cultivation in the laboratory nonmucoid, EPS(-) variants arise that have a crenated colony morphology. This change is reversible since crenated variants rapidly switch to the original m...

The B16 melanoma-derived low lung-colonizing variant B16F1 and the high lung-colonizing variant B16-F10 retained their differential lung-colonizing abilities throughout at least 35 serial s.c. transplant generations. The majority of the cells originating from solid B16-F1 tumors had a higher density than did cells originating from solid B16-F10 tumors. Cell suspensions of unselected solid 816 m...

Staphylococcus aureus is a major causative agent leading to bovine mastitis and has specific phonotypical characteristics including small colony, slow growth, and decreased hemolysis, therefore named as the small colony variants (SCVs). Out of 30 tested samples of the chronic S. aureus cases, one strain of SCVs (S. aureus SCV22) was isolated along with its parental strains (S. aureus11). S. aur...