PIXNIO / 40+ Positive free photos Positive free photos. Free for personal and commercial use. You can freely use any picture from this gallery. You are free to use the photos for personal or commercial use. PIXNIO free images: culture, gram, positive, clostridium septicum, bacteria gram, photomicrograph, gram, positive, clostridium perfringens, welchii gram, positive, clostridium botulinum, bacillus, botulinus magnified, 956x, gram, photomicrograph, numbers, clostridium gram, positive, bacteria gram, positive, clostridium tertium, bacteria, blood agar, plate colony, clostridium gram, positive, bacteria, grown, percent, blood agar, plate photograph, light, colonial, growth, gram, positive, pasteur, strain colonial, morphology, gram, positive, pasteur, strain, bacillus anthracis, bacteria bacillus anthracis, tenacity, positive, sheep, blood agar bacillus anthracis, positive, encapsulation, test, rough, colonies, blood agar, smooth, colonies, bicarbonate, agar bacillus anthracis, positive, encapsulation, test, demonstrated, two, different, agar, media