nim. "Are you heading to the lab right now?" asked Kyle. "Yes." she said. “I want to look over the Gram stain protocol one more time before we go in." "Yeah, good idea. I've been trying to memorize the steps. But it's hard." Belinda and Kyle spent the twenty minutes remaining before the start of lab going over Chapters 3 and 4 of their textbook, which listed the steps of the Gram stain and how the staining results relate to the structure of the bacterial cell wall. Kyle and Belinda took a sample of the bacteria provided by their instructor and each performed the Gram stain. They focused on their slides with the oil immersion lens. "Got it!" they said almost simultaneously, grinning proudly. "So, what do you have?" asked Belinda. "I have Gram-positive bacilli" announced Kyle with an air of triumph. "Huh? I have Gram-negative bacilli." "That's not right, we used the same sample! Let me see yours." Kyle peered through Belinda's microscope. “Your bacteria look like they have the same shape as mine, but the color is different. Mine are obviously purple, but yours look much lighter. They are definitely pink. Maybe you did something wrong." "Why me? You could have done something wrong."

Human Anatomy & Physiology (11th Edition)
11th Edition
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Author:Elaine N. Marieb, Katja N. Hoehn
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Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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Case Study: Lab Errors

Background
"Belinda!" called Kyle, running to catch up to her. Belinda turned around and waited for
him.
"Are you heading to the lab right now?" asked Kyle.
"Yes." she said. "I want to look over the Gram stain protocol one more time before we go
in."
"Yeah, good idea. I've been trying to memorize the steps. But it's hard."
Belinda and Kyle spent the twenty minutes remaining before the start of lab going over
Chapters 3 and 4 of their textbook, which listed the steps of the Gram stain and how the
staining results relate to the structure of the bacterial cell wall.
Kyle and Belinda took a sample of the bacteria provided by their instructor and each
performed the Gram stain. They focused on their slides with the oil immersion lens.
"Got it!" they said almost simultaneously, grinning proudly.
"So, what do you have?" asked Belinda.
"I have Gram-positive bacilli" announced Kyle with an air of triumph.
"Huh? I have Gram-negative bacilli."
"That's not right, we used the same sample! Let me see yours." Kyle peered through
Belinda's microscope. "Your bacteria look like they have the same shape as mine, but the
color is different. Mine are obviously purple, but yours look much lighter. They are
definitely pink. Maybe you did something wrong."
"Why me? You could have done something wrong."
Kyle looked up from Belinda's microscope. "Fair enough."
Kyle continued “I prepared a bacterial smear like we learned last week, then I added
safranin, then Gram's iodine, then decolorizer, then I added crystal violet."
"You switched up the crystal violet and the safranin," said Belinda.
"I did? Let me see that protocol again. Hmm... I guess you're right. Let me try it again."
Questions
1. Explain how the difference in the structure of the cell wall results in the different
colors after performing the Gram stain.
2. Why did Kyle's Gram stain give the wrong
result?
3. Are there any other mistakes that can result in gram-negative bacteria staining purple?
Which mistakes can result in gram-positive bacteria staining pink?
Transcribed Image Text:Background "Belinda!" called Kyle, running to catch up to her. Belinda turned around and waited for him. "Are you heading to the lab right now?" asked Kyle. "Yes." she said. "I want to look over the Gram stain protocol one more time before we go in." "Yeah, good idea. I've been trying to memorize the steps. But it's hard." Belinda and Kyle spent the twenty minutes remaining before the start of lab going over Chapters 3 and 4 of their textbook, which listed the steps of the Gram stain and how the staining results relate to the structure of the bacterial cell wall. Kyle and Belinda took a sample of the bacteria provided by their instructor and each performed the Gram stain. They focused on their slides with the oil immersion lens. "Got it!" they said almost simultaneously, grinning proudly. "So, what do you have?" asked Belinda. "I have Gram-positive bacilli" announced Kyle with an air of triumph. "Huh? I have Gram-negative bacilli." "That's not right, we used the same sample! Let me see yours." Kyle peered through Belinda's microscope. "Your bacteria look like they have the same shape as mine, but the color is different. Mine are obviously purple, but yours look much lighter. They are definitely pink. Maybe you did something wrong." "Why me? You could have done something wrong." Kyle looked up from Belinda's microscope. "Fair enough." Kyle continued “I prepared a bacterial smear like we learned last week, then I added safranin, then Gram's iodine, then decolorizer, then I added crystal violet." "You switched up the crystal violet and the safranin," said Belinda. "I did? Let me see that protocol again. Hmm... I guess you're right. Let me try it again." Questions 1. Explain how the difference in the structure of the cell wall results in the different colors after performing the Gram stain. 2. Why did Kyle's Gram stain give the wrong result? 3. Are there any other mistakes that can result in gram-negative bacteria staining purple? Which mistakes can result in gram-positive bacteria staining pink?
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