Types of microorganisms

Learning Objectives By the end of this section, you will be able to: • Describe the different types of disease reservoirs • Compare contact, vector, and vehicle modes of transmission • Identify important disease vectors • Explain the prevalence of nosocomial infections Understanding how infectious pathogens spread is critical to preventing infectious disease. Many pathogens require a living host to survive, while others may be able to persist in a dormant state outside of a living host. But having infected one host, all pathogens must also have a mechanism of transfer from one host to another or they will die when their host dies. Pathogens often have elaborate adaptations to exploit host biology, behavior, and ecology to live in and move between hosts. Hosts have evolved defenses against pathogens, but because their rates of evolution are typically slower than their pathogens (because their generation times are longer), hosts are usually at an evolutionary disadvantage. This section will explore where pathogens survive—both inside and outside hosts—and some of the many ways they move from one host to another. Reservoirs and Carriers For pathogens to persist over long periods of time they require reservoir s where they normally reside. Reservoirs can be living organisms or nonliving sites. Nonliving reservoirs can include soil and water in the environment. These may naturally harbor the organism because it may grow in that environment. These environments may also becom...

Infectious diseases are illnesses caused by harmful agents (pathogens) that get into your body. The most common causes are viruses, bacteria, fungi and parasites. Infectious diseases usually spread from person to person, through contaminated food or water and through bug bites. Some infectious diseases are minor and some are very serious. Overview What are infectious diseases? Infectious diseases are illnesses caused by harmful organisms (pathogens) that get into your body from the outside. Pathogens that cause infectious diseases are viruses, bacteria, fungi, parasites and, rarely, prions. You can get infectious diseases from other people, bug bites and contaminated food, water or soil. What’s the difference between infectious diseases and noninfectious diseases? Infectious diseases are caused by harmful organisms that get into your body from the outside, like viruses and bacteria. Noninfectious diseases aren’t caused by outside organisms, but by genetics, anatomical differences, getting older and the environment you live in. You can’t get noninfectious diseases from other people, by getting a bug bite or from your food. The flu, measles, HIV, strep throat, COVID-19 and salmonella are all examples of infectious diseases. Cancer, diabetes, congestive heart failure and Alzheimer’s disease are all examples of noninfectious diseases. What are the types of infectious diseases? Infectious diseases can be viral, bacterial, parasitic or fungal infections. There’s also a rare grou...

Figure 1.1 A veterinarian gets ready to clean a sea turtle covered in oil following the Deepwater Horizon oil spill in the Gulf of Mexico in 2010. After the spill, the population of a naturally occurring oil-eating marine bacterium called Alcanivorax borkumensis skyrocketed, helping to get rid of the oil. Scientists are working on ways to genetically engineer this bacterium to be more efficient in cleaning up future spills. (credit: modification of work by NOAA’s National Ocean Service) From boiling thermal hot springs to deep beneath the Antarctic ice, microorganisms can be found almost everywhere on earth in great quantities. Microorganisms (or microbes, as they are also called) are small organisms. Most are so small that they cannot be seen without a microscope. Most microorganisms are harmless to humans and, in fact, many are helpful. They play fundamental roles in ecosystems everywhere on earth, forming the backbone of many food webs. People use them to make biofuels, medicines, and even foods. Without microbes, there would be no bread, cheese, or beer. Our bodies are filled with microbes, and our skin alone is home to trillions of them. Although much more is known today about microbial life than ever before, the vast majority of this invisible world remains unexplored. Microbiologists continue to identify new ways that microbes benefit and threaten humans.

11 Mechanisms of Microbial Genetics • Introduction • 11.1 The Functions of Genetic Material • 11.2 DNA Replication • 11.3 RNA Transcription • 11.4 Protein Synthesis (Translation) • 11.5 Mutations • 11.6 How Asexual Prokaryotes Achieve Genetic Diversity • 11.7 Gene Regulation: Operon Theory • Summary • 14 Antimicrobial Drugs • Introduction • 14.1 History of Chemotherapy and Antimicrobial Discovery • 14.2 Fundamentals of Antimicrobial Chemotherapy • 14.3 Mechanisms of Antibacterial Drugs • 14.4 Mechanisms of Other Antimicrobial Drugs • 14.5 Drug Resistance • 14.6 Testing the Effectiveness of Antimicrobials • 14.7 Current Strategies for Antimicrobial Discovery • Summary • 23 Urogenital System Infections • Introduction • 23.1 Anatomy and Normal Microbiota of the Urogenital Tract • 23.2 Bacterial Infections of the Urinary System • 23.3 Bacterial Infections of the Reproductive System • 23.4 Viral Infections of the Reproductive System • 23.5 Fungal Infections of the Reproductive System • 23.6 Protozoan Infections of the Urogenital System • Summary • 24 Digestive System Infections • Introduction • 24.1 Anatomy and Normal Microbiota of the Digestive System • 24.2 Microbial Diseases of the Mouth and Oral Cavity • 24.3 Bacterial Infections of the Gastrointestinal Tract • 24.4 Viral Infections of the Gastrointestinal Tract • 24.5 Protozoan Infections of the Gastrointestinal Tract • 24.6 Helminthic Infections of the Gastrointestinal Tract • Summary • 25 Circulatory and Lymphatic System...

Types of Microbes The microorganisms, or microbes, that can cause disease come in different forms. Viruses and bacteria are probably the most familiar because we hear so much about them. But fungi, protozoa, and helminths are also big players in the story of infectious disease. Learn more about each of these five main categories, as well as a recently discovered one: prions.

• Biology • Microbiology • Microorganisms Microorganisms Take a moment to observe the natural world around you. Each day, you likely encounter many humans and non-human animals, such as birds, insects, lizards, and rodents. However, the natural world that is visible to us represents only a small fraction of the whole. Many organisms on our planet are too small for humans to see. These numerous tiny creatures are… Microorganisms • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Take a moment to observe the natural world around you. Each day, you likely encounter many huma...