Sem 3 BRS Micro - General Properties Of Microorganisms; /Bacteria

Bacteria form the majority of the normal flora of the large intestine. Other types of human infectious agents are not usually present except in time of disease.

Certain species of pathogenic fungi are dimorphic (i.e., existing as yeast or mold forms depending
on their environment).

N-acetyl glucosamine and N-acetyl muramic acid are polymerized to form the peptidoglycan backbone of the cell wall.

Bacteria have70S ribosomes composed of 30S and 50S subunits. Fungi and protozoa have 80S ribosomes, and prions and viruses do not have ribosomes.

Many bacterial exotoxins have an A-B subunit structure in which the B subunit is involved in binding
and the A subunit possesses biological activity inside the affected cell.

R-factor (resistance) plasmids contain genes for proteins that degrade antibiotics or alter antibiotic
transport, thus conferring antibiotic resistance. They also carry transfer genes, which facilitate their
intercellular transfer to other genomes.

Bacteriophages containing portions of host-cell DNA can introduce this genetic material into new host cells via the process of transduction.

An alcohol concentration of 70% to 95% is necessary to kill bacteria

Ordinary pili, adhesins, and the glycocalyx are three bacterial structures that are involved in adherence.

Staphylococcus aureus produces an enterotoxin and TSST-1 toxins with super-antigen activity.
Streptococcus pyogenes also produces toxins with this activity.

Autotrophic bacteria do not require organic compounds for growth because they synthesize them
from inorganic precursors.

A prophage is the intracellular DNA of a phage and is therefore resistant to protease degradation.

Fungi have ergo sterol as their dominant membrane sterol. Mycoplasmas are the only prokaryotes with sterols in their cytoplasmic membrane, but they do not synthesize their own sterols.

Superoxide dismutase is found in aerobic and facultative anaerobic bacteria. It protects them from
the toxic free radical (O2-) by combining it with a hydrogen ion to form hydrogen peroxide, which is
subsequently degraded by peroxidase.

The transcription of the lac operon is under negative control. Initiation depends on the binding of
allolactose to a repressor protein. This reaction prevents the repressor from binding to the operator
region, thus allowing RNA polymerase to bind and transcription to proceed.

A selective growth medium that contains a high salt concentration would permit bacterial growth.

Superoxide dismutase, which is present in aerobes and facultative anaerobe organisms, protects them
from the toxic O2- radical. This enzyme is not present in obligate anaerobes.

The biochemical activity of an enzyme may be regulated by binding of effect or molecules or by
biosynthetic pathway end-product feedback inhibition. Enzyme synthesis may be controlled by inducers,
attenuation sequences, or catabolite activator protein.

The plasma membrane contains the enzymes involved in oxidative phosphorylation

DNA or genetic recombination is the general term used to describe the exchange of allelic forms
of genes in bacteria or eukaryotic cells.

The transport of sugar into a bacterium frequently involves the transfer of a phosphate group to the s
ugar molecule.

These media are variants of chocolate agar and contain antibiotics that inhibit many normal respiratory
and genital bacteria but allow the growth of Neisseria species.

Lysogenic phage conversion refers to the process in which a bacterial phenotype changes as a result of the presence of a prophage. A prophage is a viral genome that has integrated into the bacterial chromosome and remains dormant until it is activated. When the prophage is activated, it can cause changes in the bacterial phenotype, such as the production of toxins or other virulence factors. This change in phenotype is the result of the expression of genes carried by the prophage, which can alter the behavior or characteristics of the bacterial host.

Clostridium tetani Exotoxin acts on synaptosomes, thereby causing hyper-reflexia of skeletal muscles.

Chlamydia and rickettsia are obligate intracellular pathogens because they depend on the host cell
to provide them with ATP.

The correct answer is Mycoplasma species. Mycoplasma species are unique bacteria that lack a cell wall, making them resistant to antibiotics that target cell wall synthesis. They also have 70S ribosomes, which are characteristic of bacteria. Chlamydia species and Rickettsia species are also bacteria, but they have cell walls. Viruses are not considered bacteria and do not possess ribosomes.

Facultative anaerobes shift from a fermentative to a respiratory metabolism in the presence of
air because the energy needs of the cell are met by consuming less glucose (Pasteur Effect) under respiratory metabolism.

B-lactamases cleave the b-lactam ring structure that is important for the antibacterial activity of penicillins,
cephalosporins, monobactams, and carbapenems.

Bacteria must be actively replicating and synthesizing protein for these compounds, which bind
to the 30S ribosomal subunit to have their bactericidal effect.

High-frequency recombination donors, which result from the integration of a fertility (F) factor in to
chromosomal DNA, are created by recombination.