Gram Stain (Mixed Bacteria)

Gram-stained smear of Staphylococcus aureus showing characteristic grape-like clusters of gram-positive cocci (dark purple).

Oil immersion — classic staphylococcal cluster morphology

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Gram-stained smear of Streptococcus pyogenes (Group A Strep) showing gram-positive cocci in chains.

Oil immersion — chains of cocci, group A beta-hemolytic streptococcus

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Gram-stained smear of Escherichia coli showing pink/red gram-negative bacilli. Uniform rod-shaped bacteria characteristic of Enterobacteriaceae.

Oil immersion — gram-negative rods, most common clinical isolate

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Gram stain showing slender gram-negative bacilli of Pseudomonas aeruginosa. Organisms appear as thin pink rods.

Oil immersion — slender gram-negative rods, opportunistic pathogen

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Gram-stained smear of Bacillus subtilis showing large gram-positive bacilli in chains. Spore-forming rod with subterminal endospores sometimes visible.

Oil immersion — large gram-positive rods in chains, spore-forming

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Ziehl-Neelsen acid-fast stain showing bright red acid-fast bacilli (AFB) of Mycobacterium tuberculosis against blue counterstain background.

Oil immersion — acid-fast bacilli, comparison with Gram stain

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Gram stain of Streptococcus pneumoniae showing lancet-shaped gram-positive diplococci with characteristically pointed ends.

Oil immersion — lancet-shaped diplococci, common cause of pneumonia

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Gram stain of Enterococcus faecalis showing gram-positive cocci in pairs and short chains. Important nosocomial pathogen.

Oil immersion — diplococci and short chains

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Gram stain of Klebsiella pneumoniae showing plump gram-negative bacilli. Mucoid capsule may appear as clear halo surrounding the organisms.

Oil immersion — encapsulated gram-negative rods

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Gram stain of Clostridium perfringens showing large gram-positive bacilli. Characteristically large, box-car shaped rods causing gas gangrene.

Oil immersion — large box-car rods, anaerobic spore-former

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Gram-stained smear of Corynebacterium diphtheriae showing pleomorphic gram-positive bacilli in palisade and V/L arrangements (Chinese letter pattern).

Oil immersion — pleomorphic rods in palisade/Chinese letter arrangements

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Gram stain of Listeria monocytogenes showing small gram-positive coccobacilli. Short rods that can resemble cocci, sometimes in short chains.

Oil immersion — small gram-positive coccobacilli, intracellular pathogen

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Gram stain of cerebrospinal fluid showing intracellular gram-negative diplococci within neutrophils, consistent with Neisseria meningitidis.

Oil immersion — intracellular gram-negative diplococci in CSF

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Gram-stained urethral discharge showing intracellular gram-negative diplococci within polymorphonuclear leukocytes. Classic finding for gonococcal urethritis.

Oil immersion — intracellular kidney-bean diplococci

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Gram stain showing gram-negative diplococci with numerous pus cells (PMNs). Characteristic finding in clinical specimen from gonococcal infection.

Oil immersion — gram-negative diplococci, respiratory pathogen

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Gram-stained sputum specimen showing numerous gram-negative bacteria with polymorphonuclear leukocytes indicating lower respiratory infection.

Oil immersion — mixed flora with PMNs, lower respiratory specimen

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Gram-stained smear of sputum prepared for microscopic observation showing mixed bacterial morphotypes and inflammatory cells.

Oil immersion — positive blood culture, cocci in clusters

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Transmission electron micrograph of Staphylococcus aureus (VISA strain) showing cell wall thickening, cell membrane, and internal cellular structures. Cross-section reveals thick peptidoglycan layer characteristic of gram-positive bacteria.

TEM thin section — cell wall thickening visible in VISA strain

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TEM cross-section of S. aureus (VISA strain) showing dividing cells with visible septum formation, thick peptidoglycan cell wall, cytoplasmic membrane, ribosomes, and nucleoid region.

TEM thin section — dividing cells with septum visible

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Electron micrograph of Staphylococcus aureus showing characteristic cocci morphology and surface detail at high magnification.

TEM — S. aureus surface and morphology detail

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TEM image showing intact population of Staphylococcus aureus cells. Individual bacteria show cell wall, membrane, and cytoplasmic contents including ribosomes and nucleoid.

TEM — intact population showing internal structures

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TEM image demonstrating phenotypic variation in S. aureus population. Cells show varying cell wall thickness and internal organization.

TEM — phenotypic variation in cell wall thickness

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Scanning electron micrograph of an E. coli colony showing rod-shaped gram-negative bacteria. Surface detail reveals smooth outer membrane characteristic of Enterobacteriaceae.

SEM — E. coli colony surface morphology

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Scanning electron micrograph of Pseudomonas aeruginosa showing rod-shaped gram-negative bacteria with visible polar flagellum and surface pili.

SEM — P. aeruginosa with flagellum and pili visible

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Scanning electron micrograph of Lactococcus lactis showing ovoid gram-positive cocci. Surface detail and cell division visible.

SEM — L. lactis cocci morphology and division

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TEM image showing emerging projections of the cellular envelope of Pseudomonas sp. Outer membrane, periplasmic space, and inner membrane visible — classic gram-negative cell wall architecture.

TEM — gram-negative envelope architecture, outer membrane projections

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Colorized scanning electron micrograph of Vibrio vulnificus showing curved rod morphology with polar flagellum. Characteristic comma-shaped gram-negative bacterium.

SEM colorized — V. vulnificus curved rod with flagellum

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Labeled diagram of a prokaryotic cell showing cell wall, cell membrane, cytoplasm, ribosomes, nucleoid (DNA), flagellum, pili, and capsule.

Reference diagram — prokaryotic cell anatomy

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Comparative diagram showing gram-positive (thick peptidoglycan, teichoic acids) vs gram-negative (thin peptidoglycan, outer membrane with LPS, periplasmic space) cell wall architecture.

Reference diagram — comparative cell wall architecture

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Detailed labeled SVG diagram of a gram-positive bacterium (S. aureus) showing capsule, thick peptidoglycan cell wall, teichoic acids, cytoplasmic membrane, nucleoid, ribosomes (70S), plasmids, mesosome, pili/fimbriae, and cytoplasm. TEM cross-section perspective.

SVG diagram — labeled cross-section of gram-positive bacterial cell

Generated — Educational SVG

Detailed labeled SVG diagram of a gram-negative bacterium (E. coli) showing outer membrane, LPS (lipopolysaccharide), periplasmic space, thin peptidoglycan layer, inner membrane, nucleoid, ribosomes (70S), plasmids, flagellum, Type I pili, inclusion bodies, and cytoplasm. TEM cross-section perspective.

SVG diagram — labeled cross-section of gram-negative bacterial cell

Generated — Educational SVG

Side-by-side comparative SVG diagram showing gram-positive (thick peptidoglycan, teichoic acids) vs gram-negative (thin peptidoglycan, outer membrane, LPS, periplasmic space, porins) cell wall architecture. Includes dimensional annotations.

SVG diagram — comparative cell wall architecture at high TEM magnification

Generated — Educational SVG