MLT 140 Homework Ch. 1 Taxonomy, the Microbial Cell, Metabolism

Which of the following are phenotypical characteristics used for classifying bacteria?

• staining characteristics

• macroscopic morphology

• nutritional needs

• all of these are correct

Answer explanation

All listed characteristics—staining, macroscopic morphology, and nutritional needs—are used to classify bacteria based on their phenotypical traits, making 'all of these are correct' the right choice.

Which of the following is written correctly using the binomial system of nomenclature?

• STAPHYLOCOCCUS aureus

• Streptococcus pyogenes

• Staphylococcus Epidermidis

• enterococcus faecalis

Answer explanation

The correct choice is 'Streptococcus pyogenes' because in the binomial nomenclature, the genus name is capitalized and italicized, while the species name is lowercase and italicized. The other options do not follow this format.

The bacterial cell (choose all that are correct):

• does not have any organelles

• contains DNA within the cytoplasm

• contains 40S and 60S ribosomal subunits

• has double-stranded DNA that is bound to histones

Answer explanation

Bacterial cells lack membrane-bound organelles and contain their DNA in the cytoplasm. They have circular, double-stranded DNA, but it is not bound to histones, and their ribosomes are 70S, not 40S and 60S.

Which of the following extensions enable the bacterial cell to attach to host cells?

• flagella

• pili

• plasmids

• ribosomes

Answer explanation

Pili are hair-like structures on the surface of bacteria that enable them to adhere to host cells, facilitating infection. Flagella are for movement, plasmids are for genetic material, and ribosomes are for protein synthesis.

The gram positive cell wall contains all of the following except:

• O antigen

• peptidoglycan

• techoic acids

Answer explanation

The gram-positive cell wall is primarily composed of peptidoglycan and contains teichoic acids. The O antigen, however, is associated with gram-negative bacteria, not gram-positive, making it the correct answer.

Exotoxins:

• are secreted by gram negative bacteria.

• may be extracellular enzymes.

• consist of LPS.

• can induce fever upon cell lysis.

Answer explanation

Exotoxins are indeed secreted by gram-negative bacteria, distinguishing them from endotoxins, which are part of the bacterial cell wall. The other options do not accurately describe exotoxins.

The morphology of those bacteria that are round and arranged in pairs is known as:

• diplococci

• streptococci

• bacilli

• coccobacilli

Answer explanation

The term 'diplococci' refers specifically to round bacteria that are arranged in pairs. 'Streptococci' are in chains, 'bacilli' are rod-shaped, and 'coccobacilli' are short rods. Therefore, 'diplococci' is the correct answer.

Gram-negative bacteria contain __________, which are not found in gram-positive bacteria.

• capsules

• periplasmic space and an outer membrane

• teichoic acids

• cross-linked peptidoglycans

Answer explanation

Gram-negative bacteria have a periplasmic space and an outer membrane, which are absent in gram-positive bacteria. This structural difference is key in distinguishing the two types of bacteria.

Which of the following is true of bacterial cells?

• The DNA is contained within a nuclear membrane.

• Their mitochondria, Golgi bodies, and endoplasmic reticulum are present in the cytoplasm

• The DNA is found in the nucleoid

• The ribosomes are 80S.

Answer explanation

Bacterial cells do not have a nuclear membrane; their DNA is located in a region called the nucleoid. The other options are incorrect as bacteria lack membrane-bound organelles like mitochondria and Golgi bodies.

Phenotypic properties used to classify bacteria include all the following, except:

• DNA relatedness

• colonial morphology

• biochemical properties

• antibiotic resistance properties

Answer explanation

DNA relatedness is a genetic property, not a phenotypic one. Phenotypic classification relies on observable traits like colonial morphology, biochemical properties, and antibiotic resistance.