Name: mycoplasmas and wall-less bacteria
Uploaded: 2025-06-12T09:23:08.000Z
Duration: 1 min 24 s
Channel: JoVE

O filo Tenericutes — comumente conhecido como micoplasmas — inclui uma única classe, Mollicutes. Essas bactérias não possuem paredes celulares e estão entre os menores organismos conhecidos. Os micoplasmas geralmente vivem em estreita associação com hospedeiros animais ou vegetais em diversos ambientes. Apesar da falta de paredes celulares, as membranas do micoplasma são resistentes à lise osmótica, em parte devido à presença de esteróis e lipoglicanos. Os micoplasmas exibem formas pleomórficas, com culturas frequentemente mostrando pequenas células cocóides, grandes células inchadas e formas filamentosas que podem ser ramificadas. Gênero Spiroplasma é helicoidal ou em forma de espiral. Falta paredes celulares e flagelos, mas exibe motilidade por meio de movimentos semelhantes a parafusos ou ondulações lentas. As espécies de Spiroplasma são encontradas em vários lugares, desde as superfícies externas de insetos e plantas até seus tecidos internos. Uma espécie notável, Spiroplasma citri, causa a doença teimosa dos citros em plantas cítricas. Outras espécies, como Mycoplasma pneumoniae, Ureaplasma urealyticum, e Metamycoplasma hominis, são patogênicas para humanos.

bactérias gram-positivas: bacilli e mycoplasma

Bacterial Phylum Tenericutes

O filo Tenericutes, que inclui a &#250;nica classe Mollicutes, compreende bact&#233;rias que n&#227;o possuem parede celular. O termo "Mollicutes" deriva do latim mollis, que significa "macio". Esses organismos est&#227;o entre os menores conhecidos e s&#227;o comumente referidos como micoplasmas, devido &#224; proemin&#234;ncia do g&#234;nero Mycoplasma, que inclui pat&#243;genos humanos bem conhecidos. Apesar de sua incapacidade de se corar como Gram-positivos (devido &#224; aus&#234;ncia de parede celular), os micoplasmas s&#227;o filogeneticamente relacionados aos Firmicutes.
Os micoplasmas frequentemente vivem em associa&#231;&#227;o muito pr&#243;xima com hospedeiros animais ou vegetais, onde a aus&#234;ncia de parede celular Gram-positiva pode ser vantajosa. Eles possuem genomas pequenos, variando de 0,6 a 2,2 milh&#245;es de pares de bases (Mbp), caracter&#237;stica t&#237;pica de simbiontes obrigat&#243;rios.
Propriedades Estruturais
A aus&#234;ncia de parede celular nos micoplasmas foi confirmada por microscopia eletr&#244;nica e an&#225;lises qu&#237;micas, que revelam a aus&#234;ncia de peptidoglicano. Embora se assemelhem a protoplastos (bact&#233;rias desprovidas de parede celular), os micoplasmas s&#227;o mais resistentes &#224; lise osm&#243;tica. Essa resist&#234;ncia &#233; parcialmente devida &#224; presen&#231;a de ester&#243;is, que estabilizam a membrana citoplasm&#225;tica. Alguns micoplasmas exigem ester&#243;is no meio de cultivo, caracter&#237;stica &#250;til para sua classifica&#231;&#227;o. Al&#233;m dos ester&#243;is, muitos micoplasmas possuem lipoglicanos&#8212;heteropolissacar&#237;deos de cadeia longa covalentemente ligados aos lip&#237;dios da membrana. Esses compostos, embutidos na membrana citoplasm&#225;tica, assemelham-se aos lipopolissacar&#237;deos de bact&#233;rias Gram-negativas, mas carecem da estrutura basal de lip&#237;dio A. Os lipoglicanos contribuem para a estabilidade da membrana e facilitam a ades&#227;o a receptores de superf&#237;cie celular animal.
Os micoplasmas exibem formas pleom&#243;rficas, com culturas frequentemente apresentando pequenas c&#233;lulas cocoides (0,2&#8211;0,3 &#956;m), c&#233;lulas inchadas e formas filamentosas ramificadas. Em &#225;gar, as col&#244;nias apresentam uma apar&#234;ncia caracter&#237;stica de "ovo frito", com um n&#250;cleo central denso embutido no meio e uma &#225;rea clara circundante. Ao contr&#225;rio das bact&#233;rias com parede celular, os micoplasmas n&#227;o s&#227;o afetados por antibi&#243;ticos que inibem a s&#237;ntese da parede celular, mas s&#227;o sens&#237;veis a antibi&#243;ticos que interferem em outros processos celulares.
Micoplasmas s&#227;o cultivados em meios complexos, frequentemente requerendo soro fresco ou fluido asc&#237;tico para fornecer ester&#243;is e &#225;cidos graxos insaturados. Embora algumas esp&#233;cies cres&#231;am mal mesmo em meios ricos, outras prosperam em meios definidos. A maioria dos micoplasmas utiliza carboidratos como fonte de energia e requer vitaminas, amino&#225;cidos, purinas e pirimidinas. O metabolismo energ&#233;tico varia entre as esp&#233;cies, com crescimento aer&#243;bio, facultativamente aer&#243;bio ou anaer&#243;bio.
Spiroplasma, um g&#234;nero de Mollicutes em forma helicoidal ou espiralada, carece tanto de parede celular quanto de flagelos, mas exibe motilidade por meio de movimento rotat&#243;rio (tipo parafuso) ou ondula&#231;&#245;es lentas. Acredita-se que essa motilidade envolva fibrilas intracelulares. Esp&#233;cies de Spiroplasma s&#227;o encontradas em diversos ambientes, incluindo carrapatos, hemolinfa e intestino de insetos, flu&#237;dos vasculares de plantas e superf&#237;cies vegetais como flores e folhas.
Uma esp&#233;cie de destaque, Spiroplasma citri, causa a doen&#231;a da teimosia dos citros e tamb&#233;m tem sido associada &#224; doen&#231;a do enfraquecimento do milho. Outros Mollicutes associados a plantas foram identificados por microscopia eletr&#244;nica, sugerindo a exist&#234;ncia de um grupo grande e diverso. Al&#233;m disso, algumas esp&#233;cies de Spiroplasma causam doen&#231;as em insetos, como a espiroplasmose em abelhas e a doen&#231;a da letargia em besouros como Melolontha.

Bactérias Gram-positivas: Bacilli e Mycoplasma

O filo Tenericutes, que inclui a &#250;nica classe Mollicutes, compreende bact&#233;rias que n&#227;o possuem parede celular. O termo "Mollicutes" deriva ...

Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Diversity

Diversidade Microbiana

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

mycoplasmas and wall-less bacteria

Mycoplasmas are wall-less bacteria in the phylum Tenericutes. This group includes the single class Mollicutes, a name that comes from the Latin mollis, meaning soft. These bacteria are among the smallest known. They are often called mycoplasmas because the genus Mycoplasma includes many well-known human pathogens.

Mycoplasmas cannot stain gram-positive because they lack cell walls. Even so, they are related to the Firmicutes. They often live closely with animal or plant hosts. Their small genomes, about 0.6 to 2.2 megabase pairs, fit the pattern seen in many obligate symbionts.

Electron microscopy and chemical tests show that mycoplasmas do not have peptidoglycan, the main material in bacterial cell walls. They can look like protoplasts, which are bacteria stripped of their walls. However, mycoplasmas are more resistant to osmotic lysis. Sterols in the cytoplasmic membrane help stabilize them, and some species need sterols in their growth media.

Many mycoplasmas also contain lipoglycans, which are long-chain heteropolysaccharides linked to membrane lipids. These molecules sit in the cytoplasmic membrane and resemble the lipopolysaccharides of gram-negative bacteria, but they do not have a lipid A backbone. Lipoglycans help stabilize the membrane and aid attachment to animal cell surface receptors. Mycoplasmas also show pleomorphic forms, so cultures may contain small coccoid cells, swollen cells, and filamentous or branched forms.

On agar, mycoplasma colonies often have a “fried egg” look. A dense center grows down into the medium, while a lighter area surrounds it. Antibiotics that block cell wall synthesis do not affect these bacteria. They are instead sensitive to antibiotics that target other cell processes. To grow them in the lab, scientists often use complex media with fresh serum or ascitic fluid. These ingredients supply sterols and unsaturated fatty acids.

Some mycoplasma species grow poorly even on rich media, while others can grow on defined media. Most use carbohydrates for energy and need vitamins, amino acids, purines, and pyrimidines. Their energy use varies, and species may be aerobic, facultative aerobic, or anaerobic.

Spiroplasma is a helical, or spiral-shaped, genus within the Mollicutes. It also lacks a cell wall and flagella, yet it moves by rotary, screw-like motion or slow undulations. This movement is thought to involve intracellular fibrils. Spiroplasma species are found in ticks, the hemolymph and gut of insects, plant vascular fluids, and on plant surfaces such as flowers and leaves.

One species, Spiroplasma citri, causes citrus stubborn disease and has also been linked to corn stunt disease. Electron microscopy has also revealed other plant-associated Mollicutes, suggesting a large and diverse group. Some Spiroplasma species also cause insect diseases, including honeybee spiroplasmosis and lethargy disease in beetles such as Melolontha.

Mycoplasmas and Wall-Less Bacteria

three-domain system of life

How rRNA Reshaped Life's Domains

Ribosomal RNA, or rRNA, changed how scientists classify life. Sequence analysis showed three major groups of cells: eukaryotes, bacteria, and archaea. In 1978, Carl R. Woese proposed domains as a taxonomic level above kingdoms to separate these groups. Woese also showed that archaea and bacteria are not the same, even though they can look similar. The three domains differ in rRNA, membrane lipid structure, transfer RNA, and sensitivity to antibiotics. These differences helped scientists build...

microbial classification system

Naming and Ranking Microbes

Microbial classification organizes bacteria and archaea into ranked groups based on shared traits and evolutionary relationships. Scientists use phenotypic similarities, which are visible or measurable traits, and genotypic data, which comes from genetic information. The result is a hierarchy that helps place each organism in a clear taxonomic order. The ranking system starts with species and moves upward through genus, family, order, class, and finally domain. A species can include one or...

methods of classification and identification

methods-of-classification-and-identification

Bacterial ID Through Lab Tests

Bacterial identification uses lab tests to sort microorganisms by visible traits, chemical activity, and genetic makeup. These methods help scientists and clinicians recognize bacteria and understand how closely related they are. Traditional morphology is useful, but it can be limited for closely related or very simple organisms. Morphological features give an early clue about a bacterium. Cell shape, flagella, and endospores can all help with basic classification. Differential stains such as...

modern molecular taxonomy

DNA Tools for Identifying Bacteria

DNA-based methods help scientists identify and compare bacteria with much greater precision. As sequencing becomes faster and less expensive, these tools are used in clinical, environmental, and evolutionary studies. They let researchers tell related strains apart and track how microbes spread. One important method is multilocus sequence typing, or MLST. It examines several housekeeping genes, which are essential chromosomal genes that support basic cell functions. About 450-base-pair...

applications of molecular taxonomy

Molecular Taxonomy in Bacterial Research

Molecular taxonomy in bacterial research uses DNA sequencing and DNA fingerprinting to classify bacteria more precisely. These molecular tools help scientists study bacterial diversity, evolutionary relationships, and ecological roles. They have changed how researchers identify and compare bacteria in both health and environmental studies. One major use of molecular taxonomy is resolving taxonomic ambiguities, or unclear classification cases. It can separate closely related bacteria that were...

bacterial phylum proteobacteria

Proteobacteria Classes and Their Key Roles

Proteobacteria are a large and diverse phylum of Gram-negative bacteria. They have an outer membrane that contains lipopolysaccharides. Many of them use different ways to get energy, including phototrophy, chemolithotrophy, and heterotrophy. They live in soil, water, and host-associated environments. This phylum is divided into six classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, and Zetaproteobacteria. Each class includes...

bacterial phylum chlamydiae

Chlamydiae Life Cycle and Host Infection

Chlamydiae are bacteria that live inside eukaryotic host cells. The phylum Chlamydiae, also called Chlamydiota, contains a single order, Chlamydiales. These bacteria are obligate intracellular parasites, which means they must enter host cells to survive and grow. Members of this group are usually very small cocci, about 0.5 μm across. They also have reduced genomes, usually between 0.55 and 1 Mbp. This limited genome fits their highly specialized way of life and their dependence on host...

bacterial phylum planctomycetes 

Planctomycetes Cell Structure and Life Cycle

Planctomycetes are a group of gram-negative bacteria known for unusual cell structures and a distinctive life cycle. They are mainly placed in two orders, Planctomycetales and Brocadiales. Many cells show stalks or other appendages and often appear in rosette groups. A key feature of these bacteria is their cell envelope. Planctomycetes have an S-layer, a surface layer that is relatively uncommon in bacteria. They also divide by budding, which is different from the simple cell split seen in...

bacterial phylum verrucomicrobiota

Verrucomicrobiota Cell Structure and Traits

Verrucomicrobiota are a bacterial phylum with several recognized orders, and most species belong to Verrucomicrobiotales. Many members are aerobic or facultatively aerobic, which means they can use oxygen but may also grow without it. They can also ferment sugars. One exception is the genus Methylacidiphilum, which contains aerobic methanotrophs, bacteria that use methane and oxygen. These bacteria live in many different places. They are found in freshwater, marine habitats, forest soils, and...

bacterial phylum spirochaetes

Spirochete Shape, Motion, and Disease

Spirochetes are a group of gram-negative bacteria with a thin, flexible, tightly coiled shape. They live in aquatic sediments and in animals. Some species are harmless, while others cause diseases such as syphilis and Lyme disease. A key feature of spirochetes is their movement. They use endoflagella, which are flagella located inside the periplasm, the space under the outer layer of the cell. These endoflagella attach at the cell poles and run along the length of the bacterium inside a...

bacterial phylum cyanobacteria

Cyanobacteria and Oxygenic Photosynthesis

Cyanobacteria are oxygenic, phototrophic bacteria that helped change Earth&amp;#8217;s atmosphere from low in oxygen to oxygen-rich billions of years ago. They are also very diverse in shape and size. Some are unicellular, while others grow as filaments. Cell size can range from 0.5 µm to 100 µm. Scientists group cyanobacteria into five major types. Chroococcales are unicellular and divide by binary fission. Pleurocapsales are also unicellular, but they divide by multiple fission.

bacterial phylum actinobacteria

Actinobacteria: Soil Bacteria and Cheese

Actinobacteria include several gram-positive bacteria that are common in soil and food production. This group includes coryneform bacteria, propionic acid bacteria, mycobacteria, and actinomycetes. Each group has a different shape, growth pattern, and role. Coryneform bacteria are aerobic, nonmotile rods that often look irregular, club-shaped, or V-shaped. Their V-shape comes from snapping division. In this process, the inner cell wall forms the cross-wall first, while the outer wall stays...

bacterial phylum firmicutes

Firmicutes: Bacteria, Fermentation, and Spores

Firmicutes are a diverse phylum of Gram-positive bacteria with low GC content in their genomes. They include both monoderm and diderm cell envelopes, which points to a complex evolutionary history. Their members show wide variation in shape, metabolism, and ecological role. Three major orders help show this diversity: Lactobacillales, Clostridiales, and Bacillales. Lactobacillales include lactic acid bacteria, which are fermentative organisms that make lactic acid as their main product. These...

bacterial phylum bacteroidota

Gut and Environment Bacteria in Bacteroidota

Bacteroidota is a bacterial phylum with more than 700 species. It includes four main orders: Bacteroidales, Cytophagales, Flavobacteriales, and Sphingobacteriales. These bacteria are gram-negative, do not form spores, and are usually rod-shaped. They can be aerobic or fermentative, and some use gliding motility while others are nonmotile or move with flagella. Bacteroidales includes obligately anaerobic, fermentative bacteria. The genus Bacteroides is especially important because it lives in...

anoxygenic phototrophic bacteria

Sulfur-Using Bacteria That Harvest Light

Anoxygenic phototrophic bacteria are light-harvesting bacteria that do not release oxygen during photosynthesis. They include purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, green nonsulfur bacteria, heliobacteria, and Chloracidobacterium thermophilum. These groups belong to the Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Chlorobi, Chloroflexi, Firmicutes, and Acidobacteria lineages, and each group has its own habitat and way of using light. Purple...

hyperthermophilic bacteria

Heat-Loving Bacteria and Their Enzymes

Hyperthermophilic bacteria live in extreme heat and show unusual adaptations that help them survive. Several of these species come from the Domain Bacteria and are found in hot springs and hydrothermal vents. Their biology helps explain how life can function in very hot environments. Thermotoga species are rod-shaped, gram-negative, non-sporulating hyperthermophiles. They form a sheath-like outer layer called a toga. These bacteria ferment sugars or starch and produce lactate, acetate, carbon...

bacterial phylum tenericutes

Mycoplasmas are wall-less bacteria in the phylum Tenericutes. This group includes the single class Mollicutes, a name that comes from the Latin mollis, meaning soft. These bacteria are among the smallest known. They are often called mycoplasmas because the genus Mycoplasma includes many well-known human pathogens. Mycoplasmas cannot stain gram-positive because they lack cell walls. Even so, they are related to the Firmicutes. They often live closely with animal or plant hosts. Their small...

other unique bacteria

Magnetotactic and DNA-Resistant Bacteria

Magnetotactic bacteria move using Earth’s magnetic field, and some bacteria are known for extreme DNA repair. These unusual microbes show two very different survival strategies. One uses magnetic particles to guide movement. The other can recover after severe radiation damage. Magnetotaxis is the directed movement seen in magnetic bacteria. It depends on magnetosomes, which are chains of magnetic particles made of magnetite (Fe₃O₄) or greigite (Fe₃S₄). A protein scaffold keeps these particles...

overview of archaea

Archaea Cell Structure and Metabolism

Archaea are a unique domain of life with cell structures and metabolic strategies that set them apart from bacteria and eukaryotes. They were named after the Archaean eon and are important for understanding both early life and modern biotechnology. One key feature of archaea is their membrane chemistry. Their membranes contain ether-linked isoprenoid lipids, which help them stay stable in extreme conditions such as high heat and chemical stress. Archaea also have RNA polymerases that are more...

diversity of archaea i

Archaea Extremes: Euryarchaeota

Euryarchaeota is a major phylum of Archaea, a domain of single-celled microorganisms. Archaea are grouped into five major phyla based on genetic and biochemical traits: Euryarchaeota, Crenarchaeota, Thaumarchaeota, Korarchaeota, and Nanoarchaeota. Among them, Euryarchaeota stands out for its wide range of shapes, metabolism, and habitat use. Members of this phylum can have rod or cocci shapes. Their metabolism may be strictly aerobic or strictly anaerobic, which lets them live in both...

diversity of archaea ii

New Archaea Phyla and Their Roles

Archaea are one of the three domains of life, and their diversity includes species that live in both extreme and moderate environments. For a long time, most known archaea were grouped into two major phyla: Euryarchaeota and Crenarchaeota. Recent molecular studies have added three more phyla to this picture: Thaumarchaeota, Nanoarchaeota, and Korarchaeota. Thaumarchaeota are mesophilic archaea, which means they live in moderate conditions. They are found in soils, lakes, and marine regions. A...

diversity of archaea iii

Crenarchaeota in Extreme Hot Springs

Crenarchaeota are a major group of Archaea known for living in extreme heat and acidity. They are found in sulfur-rich hot springs, volcanic systems, and submarine hydrothermal vents. Many of these habitats reach temperatures above 100°C. Their survival in these conditions gives clues about life on early Earth. Crenarchaeota also show a wide range of cell shapes. Some form filaments, while others have irregular discs or lobed cocci, which are round cells with lobes. Scientists place them in...

diversity of archaea iv

How Hyperthermophilic Archaea Survive Heat

Hyperthermophilic archaea are heat-loving extremophiles that live at temperatures above 80°C. They are often found in hydrothermal vents and volcanic soils, where the heat can be higher than the boiling point of water. At these temperatures, the proteins, membranes, and DNA of most organisms would break down. These archaea survive because their cell membranes are built differently. Their membranes contain a monolayer of biphytanyl tetraether lipids, which helps resist thermal damage. This...

overview of fungi

Fungi Structure, Reproduction, and Roles

Fungi are eukaryotes that are more closely related to animals than to other eukaryotes. Their cell walls contain chitin, a polysaccharide that gives strength, and glucans, which add flexibility and support. Some fungi also use mannans and galactosans in place of, or along with, chitin. These features help fungi live in acidic places and survive high osmotic pressure. Fungi can be unicellular, like yeasts, or multicellular. In multicellular fungi, the body forms a mycelium, which is a branching...

fungal group zygomycota

Zygomycota: Spores, Hyphae, and Roles

Zygomycota are a former fungal group made up mostly of terrestrial molds that act as decomposers. Recent phylogenetic studies now place them in two major clades: Mucoromycota and Zoopagomycota. Mucoromycota includes many symbiotic species, while Zoopagomycota is made up mainly of parasitic and pathogenic fungi. These fungi have coenocytic hyphae, which are filaments without septa, or cross walls. That structure allows cytoplasm and organelles to move through the hyphae in one continuous stream.

fungal phylum microsporidia

Microsporidia Spores and Host Infection

Microsporidia are unicellular fungi that live as obligate intracellular parasites. They were first classified as protists, but phylogenetic, molecular, and structural evidence later linked them to the Chytridiomycota. These non-motile organisms infect many animal hosts, including humans, and depend heavily on the host cell to survive. Their cells are very small, usually 2 to 5 micrometers wide. Microsporidia form spores with a chitin shell, which helps them resist the outside environment. The...

fungal phylum ascomycota

Ascomycota: Sac Fungi and Their Spore Cycle

Ascomycota are sac fungi with a wide range of forms and roles. This fungal phylum includes unicellular yeasts and filamentous molds such as Aspergillus and Penicillium. They live in aquatic and terrestrial habitats and have major ecological and economic importance. A key feature of ascomycetes is the ascus, a sac-like structure that contains haploid ascospores. These fungi can reproduce sexually and asexually. Sexual reproduction starts with plasmogamy, the fusion of cytoplasm from two...

fungal phylum basidiomycota

Basidiomycota: Mushrooms, Spores, and Ecological Roles

Basidiomycota is a major group of fungi that includes mushrooms, puffballs, decomposers, symbionts, plant pathogens, and some edible species. These fungi matter in ecosystems, agriculture, and medicine. A key feature of this phylum is the basidium, a small club-shaped structure that makes basidiospores. Many basidiomycetes form visible fruiting bodies called basidiocarps. The life cycle starts when a haploid basidiospore germinates into monokaryotic mycelium. When two compatible mycelia fuse,...

overview of algae

Algae Structure, Habitats, and Reproduction

Algae are simple eukaryotic photoautotrophs that live in many habitats and show a wide range of body forms. They contain chlorophyll and carry out oxygenic photosynthesis. They belong to the kingdom Archaeplastida, which also includes red and green algae and land plants. Unlike other protists with chloroplasts from secondary endosymbiosis, red and green algae came from primary endosymbiotic events. Algae can look very different from one another. Some are large brown kelp in coastal waters,...

red algae

Red Algae Pigments, Shapes, and Uses

Red algae are phototrophic organisms found mostly in marine environments. Some species also live in freshwater or on land. They may be unicellular or multicellular, and some multicellular forms grow large enough to be seen easily. These algae contain chlorophyll a, but their chloroplasts do not contain chlorophyll b. Instead, they use phycobiliproteins, which are light-harvesting pigments like those found in cyanobacteria. The red color seen in many species comes from phycoerythrin, an...

green algae

Green Algae: Forms, Habitats, and Roles

Green algae are photosynthetic organisms with chlorophylls a and b in their chloroplasts. These pigments give them a green color. They differ from red algae because they lack phycobiliproteins, the pigments that produce red or blue-green tones in red algae. In pigment makeup, green algae are close to plants, and they share a close evolutionary relationship with them. Green algae belong to Phylum Chlorophyta in the Kingdom Archaeplastida. They are usually divided into two main groups:...

other algae

Stramenopile Algae: Diatoms, Golden, Brown

Stramenopile algae include diatoms, golden algae, and brown algae. These phototrophic microorganisms have flagella with many short, hairlike extensions. That feature gave the group its name, which comes from Latin words meaning “straw” and “hair.” Diatoms are unicellular, photosynthetic eukaryotes, and more than 200 genera are known. They are important parts of plankton in both marine and freshwater ecosystems. Their most distinctive feature is a silica-based cell wall called a frustule. This...

overview of protists

Protist Diversity, Movement, and Survival

Protists are diverse eukaryotic microorganisms with many ways to move, eat, and survive. They do not have the specialized tissues of plants and animals or the chitinous cell walls of fungi. Their early split within Eukarya led to major structural, functional, and ecological diversity. Scientists group protists into supergroups based on genetic analysis and shared structures. These groups include Archaeplastida, Excavata, Amoebozoa, Rhizaria, Alveolata, and Stramenopiles. This classification...

diversity of protists i

Excavata Protists and Their Adaptations

Excavata protists show many different ways of living, from photosynthesis to parasitism. This group includes organisms that can use chemical energy, light, or both. Some also live in low-oxygen, or anaerobic, environments where they survive without normal oxygen-based metabolism. Among the main Excavata groups are diplomonads and parabasalids. These are flagellated protists, meaning they move with whip-like tails, and they lack mitochondria and chloroplasts. They often live in anoxic habitats,...

diversity of protists ii

Alveolates: Ciliates, Dinoflagellates, Apicomplexans

Alveolates are protists with tiny sacs called alveoli beneath the cell membrane. These sacs may help control water balance by limiting how much water moves in and out of the cell. In dinoflagellates, alveoli may also act like armor plates. The three main alveolate groups are ciliates, dinoflagellates, and apicomplexans. Ciliates move with cilia, which are short hair-like structures that can cover the whole cell or appear in rows or tufts. One well-known ciliate is Paramecium, which uses cilia...

diversity of protists iii

Rhizaria: Pseudopods, Tests, and Skeletons

Rhizaria are unicellular protists with threadlike pseudopodia, which are thin cytoplasmic extensions used for movement and feeding. Their amoeboid shape once caused taxonomic confusion, but molecular phylogenetics has since shown where they fit on the evolutionary tree. This group includes Chlorarachniophyta, Radiolaria, and Foraminifera, and each lineage has adapted to a different ecological niche and metabolic strategy. Chlorarachniophyta are unicellular phototrophic protists found in marine...

diversity of protists iv

Amoebozoa: Movement and Life Cycles

Amoebozoa are a diverse group of terrestrial and aquatic protists. They move and feed with lobe-shaped pseudopodia. This feature sets them apart from Rhizaria, which have threadlike pseudopodia. The group includes gymnamoebas, entamoebas, and the plasmodial and cellular slime molds. Phylogenetic evidence also shows that Amoebozoa split from a lineage that later gave rise to fungi and animals. Gymnamoebas are free-living protists that live in water and soil. They move by amoeboid movement,...

key terms and concepts

Learn how mycoplasmas lack cell walls, survive with sterols, form “fried egg” colonies, and include Spiroplasma species that infect plants and insects.

Mycoplasmas and Wall-Less Bacteria | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Mycoplasmas and Wall-Less Bacteria

Description

Transcript

Tags